diff --git a/lib/compiler.js b/lib/compiler.js
index cb348ab..a4008ef 100644
--- a/lib/compiler.js
+++ b/lib/compiler.js
@@ -198,6 +198,8 @@ PEG.Grammar.Choice = function(alternatives) {
   this._alternatives = alternatives;
 };
 
+PEG.Grammar.Optional = function(element) { this._element = element; };
+
 PEG.Grammar.ZeroOrMore = function(element) { this._element = element; };
 
 PEG.Grammar.OneOrMore = function(element) { this._element = element; };
@@ -243,6 +245,9 @@ PEG.Grammar.extendNodes("checkReferencedRulesExist", {
       });
     },
 
+  Optional:
+    function(grammar) { this._element.checkReferencedRulesExist(grammar); },
+
   ZeroOrMore:
     function(grammar) { this._element.checkReferencedRulesExist(grammar); },
 
@@ -295,6 +300,11 @@ PEG.Grammar.extendNodes("checkNoLeftRecursion", {
       });
     },
 
+  Optional:
+    function(grammar, appliedRules) {
+      this._element.checkNoLeftRecursion(grammar, appliedRules);
+    },
+
   ZeroOrMore:
     function(grammar, appliedRules) {
       this._element.checkNoLeftRecursion(grammar, appliedRules);
@@ -862,6 +872,20 @@ PEG.Grammar.Choice.prototype.compile = function(resultVar) {
   return code;
 };
 
+PEG.Grammar.Optional.prototype.compile = function(resultVar) {
+  var elementResultVar = PEG.Compiler.generateUniqueIdentifier("result");
+
+  return PEG.Compiler.formatCode(
+    "${elementCode}",
+    "var ${resultVar} = ${elementResultVar} !== null ? ${elementResultVar} : '';",
+    {
+      elementCode:      this._element.compile(elementResultVar),
+      elementResultVar: elementResultVar,
+      resultVar:        resultVar
+    }
+  );
+};
+
 PEG.Grammar.ZeroOrMore.prototype.compile = function(resultVar) {
   var elementResultVar = PEG.Compiler.generateUniqueIdentifier("result");
 
diff --git a/lib/metagrammar.js b/lib/metagrammar.js
index 867c330..d76f9d6 100644
--- a/lib/metagrammar.js
+++ b/lib/metagrammar.js
@@ -426,9 +426,7 @@ PEG.grammarParser = (function(){
         this._pos = savedPos9;
       }
       var result50 = result51 !== null
-        ? (function() { 
-              return new PEG.Grammar.Choice([(arguments[0]), new PEG.Grammar.Literal("")]);
-             }).apply(this, result51)
+        ? (function() {  return new PEG.Grammar.Optional((arguments[0]));    }).apply(this, result51)
         : null;
       if (result50 !== null) {
         var result40 = result50;
@@ -1920,32 +1918,15 @@ PEG.grammarParser = (function(){
       }
       if (result195 !== null) {
         if (this._input.substr(this._pos, 1) === "^") {
-          var result204 = "^";
+          var result203 = "^";
           this._pos += 1;
         } else {
-          var result204 = null;
+          var result203 = null;
           if (context.reportMatchFailures) {
             this._matchFailed(this._quoteString("^"));
           }
         }
-        if (result204 !== null) {
-          var result196 = result204;
-        } else {
-          if (this._input.substr(this._pos, 0) === "") {
-            var result203 = "";
-            this._pos += 0;
-          } else {
-            var result203 = null;
-            if (context.reportMatchFailures) {
-              this._matchFailed(this._quoteString(""));
-            }
-          }
-          if (result203 !== null) {
-            var result196 = result203;
-          } else {
-            var result196 = null;;
-          };
-        }
+        var result196 = result203 !== null ? result203 : '';
         if (result196 !== null) {
           var result197 = [];
           var result202 = this._parse_classCharacterRange(context);
@@ -2036,34 +2017,34 @@ PEG.grammarParser = (function(){
       
       
       var savedPos35 = this._pos;
-      var result207 = this._parse_bracketDelimitedCharacter(context);
-      if (result207 !== null) {
+      var result206 = this._parse_bracketDelimitedCharacter(context);
+      if (result206 !== null) {
         if (this._input.substr(this._pos, 1) === "-") {
-          var result208 = "-";
+          var result207 = "-";
           this._pos += 1;
         } else {
-          var result208 = null;
+          var result207 = null;
           if (context.reportMatchFailures) {
             this._matchFailed(this._quoteString("-"));
           }
         }
-        if (result208 !== null) {
-          var result209 = this._parse_bracketDelimitedCharacter(context);
-          if (result209 !== null) {
-            var result206 = [result207, result208, result209];
+        if (result207 !== null) {
+          var result208 = this._parse_bracketDelimitedCharacter(context);
+          if (result208 !== null) {
+            var result205 = [result206, result207, result208];
           } else {
-            var result206 = null;
+            var result205 = null;
             this._pos = savedPos35;
           }
         } else {
-          var result206 = null;
+          var result205 = null;
           this._pos = savedPos35;
         }
       } else {
-        var result206 = null;
+        var result205 = null;
         this._pos = savedPos35;
       }
-      var result205 = result206 !== null
+      var result204 = result205 !== null
         ? (function() { 
           if ((arguments[0]).charCodeAt(0) > (arguments[2]).charCodeAt(0)) {
             throw new this.SyntaxError(
@@ -2078,16 +2059,16 @@ PEG.grammarParser = (function(){
           return PEG.RegExpUtils.quoteForClass((arguments[0]))
             + "-"
             + PEG.RegExpUtils.quoteForClass((arguments[2]));
-         }).apply(this, result206)
+         }).apply(this, result205)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result205
+        result:  result204
       };
-      return result205;
+      return result204;
     },
     
     _parse_classCharacter: function(context) {
@@ -2101,20 +2082,20 @@ PEG.grammarParser = (function(){
       var pos = this._pos;
       
       
-      var result211 = this._parse_bracketDelimitedCharacter(context);
-      var result210 = result211 !== null
+      var result210 = this._parse_bracketDelimitedCharacter(context);
+      var result209 = result210 !== null
         ? (function() { 
           return PEG.RegExpUtils.quoteForClass((arguments[0]));
-         }).call(this, result211)
+         }).call(this, result210)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result210
+        result:  result209
       };
-      return result210;
+      return result209;
     },
     
     _parse_bracketDelimitedCharacter: function(context) {
@@ -2128,31 +2109,31 @@ PEG.grammarParser = (function(){
       var pos = this._pos;
       
       
-      var result218 = this._parse_simpleBracketDelimitedCharacter(context);
-      if (result218 !== null) {
-        var result212 = result218;
+      var result217 = this._parse_simpleBracketDelimitedCharacter(context);
+      if (result217 !== null) {
+        var result211 = result217;
       } else {
-        var result217 = this._parse_simpleEscapeSequence(context);
-        if (result217 !== null) {
-          var result212 = result217;
+        var result216 = this._parse_simpleEscapeSequence(context);
+        if (result216 !== null) {
+          var result211 = result216;
         } else {
-          var result216 = this._parse_zeroEscapeSequence(context);
-          if (result216 !== null) {
-            var result212 = result216;
+          var result215 = this._parse_zeroEscapeSequence(context);
+          if (result215 !== null) {
+            var result211 = result215;
           } else {
-            var result215 = this._parse_hexEscapeSequence(context);
-            if (result215 !== null) {
-              var result212 = result215;
+            var result214 = this._parse_hexEscapeSequence(context);
+            if (result214 !== null) {
+              var result211 = result214;
             } else {
-              var result214 = this._parse_unicodeEscapeSequence(context);
-              if (result214 !== null) {
-                var result212 = result214;
+              var result213 = this._parse_unicodeEscapeSequence(context);
+              if (result213 !== null) {
+                var result211 = result213;
               } else {
-                var result213 = this._parse_eolEscapeSequence(context);
-                if (result213 !== null) {
-                  var result212 = result213;
+                var result212 = this._parse_eolEscapeSequence(context);
+                if (result212 !== null) {
+                  var result211 = result212;
                 } else {
-                  var result212 = null;;
+                  var result211 = null;;
                 };
               };
             };
@@ -2164,9 +2145,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result212
+        result:  result211
       };
-      return result212;
+      return result211;
     },
     
     _parse_simpleBracketDelimitedCharacter: function(context) {
@@ -2185,75 +2166,75 @@ PEG.grammarParser = (function(){
       var savedReportMatchFailuresVar3 = context.reportMatchFailures;
       context.reportMatchFailures = false;
       if (this._input.substr(this._pos, 1) === "]") {
-        var result226 = "]";
+        var result225 = "]";
         this._pos += 1;
       } else {
-        var result226 = null;
+        var result225 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("]"));
         }
       }
-      if (result226 !== null) {
-        var result223 = result226;
+      if (result225 !== null) {
+        var result222 = result225;
       } else {
         if (this._input.substr(this._pos, 1) === "\\") {
-          var result225 = "\\";
+          var result224 = "\\";
           this._pos += 1;
         } else {
-          var result225 = null;
+          var result224 = null;
           if (context.reportMatchFailures) {
             this._matchFailed(this._quoteString("\\"));
           }
         }
-        if (result225 !== null) {
-          var result223 = result225;
+        if (result224 !== null) {
+          var result222 = result224;
         } else {
-          var result224 = this._parse_eolChar(context);
-          if (result224 !== null) {
-            var result223 = result224;
+          var result223 = this._parse_eolChar(context);
+          if (result223 !== null) {
+            var result222 = result223;
           } else {
-            var result223 = null;;
+            var result222 = null;;
           };
         };
       }
       context.reportMatchFailures = savedReportMatchFailuresVar3;
-      if (result223 === null) {
-        var result221 = '';
+      if (result222 === null) {
+        var result220 = '';
       } else {
-        var result221 = null;
+        var result220 = null;
         this._pos = savedPos37;
       }
-      if (result221 !== null) {
+      if (result220 !== null) {
         if (this._input.length > this._pos) {
-          var result222 = this._input.charAt(this._pos);
+          var result221 = this._input.charAt(this._pos);
           this._pos++;
         } else {
-          var result222 = null;
+          var result221 = null;
           if (context.reportMatchFailures) {
             this._matchFailed('any character');
           }
         }
-        if (result222 !== null) {
-          var result220 = [result221, result222];
+        if (result221 !== null) {
+          var result219 = [result220, result221];
         } else {
-          var result220 = null;
+          var result219 = null;
           this._pos = savedPos36;
         }
       } else {
-        var result220 = null;
+        var result219 = null;
         this._pos = savedPos36;
       }
-      var result219 = result220 !== null
-        ? (function() {  return (arguments[1]);  }).apply(this, result220)
+      var result218 = result219 !== null
+        ? (function() {  return (arguments[1]);  }).apply(this, result219)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result219
+        result:  result218
       };
-      return result219;
+      return result218;
     },
     
     _parse_simpleEscapeSequence: function(context) {
@@ -2269,87 +2250,87 @@ PEG.grammarParser = (function(){
       
       var savedPos38 = this._pos;
       if (this._input.substr(this._pos, 1) === "\\") {
-        var result229 = "\\";
+        var result228 = "\\";
         this._pos += 1;
       } else {
-        var result229 = null;
+        var result228 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("\\"));
         }
       }
-      if (result229 !== null) {
+      if (result228 !== null) {
         var savedPos39 = this._pos;
         var savedReportMatchFailuresVar4 = context.reportMatchFailures;
         context.reportMatchFailures = false;
-        var result236 = this._parse_digit(context);
-        if (result236 !== null) {
-          var result232 = result236;
+        var result235 = this._parse_digit(context);
+        if (result235 !== null) {
+          var result231 = result235;
         } else {
           if (this._input.substr(this._pos, 1) === "x") {
-            var result235 = "x";
+            var result234 = "x";
             this._pos += 1;
           } else {
-            var result235 = null;
+            var result234 = null;
             if (context.reportMatchFailures) {
               this._matchFailed(this._quoteString("x"));
             }
           }
-          if (result235 !== null) {
-            var result232 = result235;
+          if (result234 !== null) {
+            var result231 = result234;
           } else {
             if (this._input.substr(this._pos, 1) === "u") {
-              var result234 = "u";
+              var result233 = "u";
               this._pos += 1;
             } else {
-              var result234 = null;
+              var result233 = null;
               if (context.reportMatchFailures) {
                 this._matchFailed(this._quoteString("u"));
               }
             }
-            if (result234 !== null) {
-              var result232 = result234;
+            if (result233 !== null) {
+              var result231 = result233;
             } else {
-              var result233 = this._parse_eolChar(context);
-              if (result233 !== null) {
-                var result232 = result233;
+              var result232 = this._parse_eolChar(context);
+              if (result232 !== null) {
+                var result231 = result232;
               } else {
-                var result232 = null;;
+                var result231 = null;;
               };
             };
           };
         }
         context.reportMatchFailures = savedReportMatchFailuresVar4;
-        if (result232 === null) {
-          var result230 = '';
+        if (result231 === null) {
+          var result229 = '';
         } else {
-          var result230 = null;
+          var result229 = null;
           this._pos = savedPos39;
         }
-        if (result230 !== null) {
+        if (result229 !== null) {
           if (this._input.length > this._pos) {
-            var result231 = this._input.charAt(this._pos);
+            var result230 = this._input.charAt(this._pos);
             this._pos++;
           } else {
-            var result231 = null;
+            var result230 = null;
             if (context.reportMatchFailures) {
               this._matchFailed('any character');
             }
           }
-          if (result231 !== null) {
-            var result228 = [result229, result230, result231];
+          if (result230 !== null) {
+            var result227 = [result228, result229, result230];
           } else {
-            var result228 = null;
+            var result227 = null;
             this._pos = savedPos38;
           }
         } else {
-          var result228 = null;
+          var result227 = null;
           this._pos = savedPos38;
         }
       } else {
-        var result228 = null;
+        var result227 = null;
         this._pos = savedPos38;
       }
-      var result227 = result228 !== null
+      var result226 = result227 !== null
         ? (function() { 
           return (arguments[2])
             .replace("b", "\b")
@@ -2358,16 +2339,16 @@ PEG.grammarParser = (function(){
             .replace("r", "\r")
             .replace("t", "\t")
             .replace("v", "\x0B") // IE does not recognize "\v".
-         }).apply(this, result228)
+         }).apply(this, result227)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result227
+        result:  result226
       };
-      return result227;
+      return result226;
     },
     
     _parse_zeroEscapeSequence: function(context) {
@@ -2383,47 +2364,47 @@ PEG.grammarParser = (function(){
       
       var savedPos40 = this._pos;
       if (this._input.substr(this._pos, 2) === "\\0") {
-        var result239 = "\\0";
+        var result238 = "\\0";
         this._pos += 2;
       } else {
-        var result239 = null;
+        var result238 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("\\0"));
         }
       }
-      if (result239 !== null) {
+      if (result238 !== null) {
         var savedPos41 = this._pos;
         var savedReportMatchFailuresVar5 = context.reportMatchFailures;
         context.reportMatchFailures = false;
-        var result241 = this._parse_digit(context);
+        var result240 = this._parse_digit(context);
         context.reportMatchFailures = savedReportMatchFailuresVar5;
-        if (result241 === null) {
-          var result240 = '';
+        if (result240 === null) {
+          var result239 = '';
         } else {
-          var result240 = null;
+          var result239 = null;
           this._pos = savedPos41;
         }
-        if (result240 !== null) {
-          var result238 = [result239, result240];
+        if (result239 !== null) {
+          var result237 = [result238, result239];
         } else {
-          var result238 = null;
+          var result237 = null;
           this._pos = savedPos40;
         }
       } else {
-        var result238 = null;
+        var result237 = null;
         this._pos = savedPos40;
       }
-      var result237 = result238 !== null
-        ? (function() {  return "\0";  }).apply(this, result238)
+      var result236 = result237 !== null
+        ? (function() {  return "\0";  }).apply(this, result237)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result237
+        result:  result236
       };
-      return result237;
+      return result236;
     },
     
     _parse_hexEscapeSequence: function(context) {
@@ -2439,45 +2420,45 @@ PEG.grammarParser = (function(){
       
       var savedPos42 = this._pos;
       if (this._input.substr(this._pos, 2) === "\\x") {
-        var result244 = "\\x";
+        var result243 = "\\x";
         this._pos += 2;
       } else {
-        var result244 = null;
+        var result243 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("\\x"));
         }
       }
-      if (result244 !== null) {
-        var result245 = this._parse_hexDigit(context);
-        if (result245 !== null) {
-          var result246 = this._parse_hexDigit(context);
-          if (result246 !== null) {
-            var result243 = [result244, result245, result246];
+      if (result243 !== null) {
+        var result244 = this._parse_hexDigit(context);
+        if (result244 !== null) {
+          var result245 = this._parse_hexDigit(context);
+          if (result245 !== null) {
+            var result242 = [result243, result244, result245];
           } else {
-            var result243 = null;
+            var result242 = null;
             this._pos = savedPos42;
           }
         } else {
-          var result243 = null;
+          var result242 = null;
           this._pos = savedPos42;
         }
       } else {
-        var result243 = null;
+        var result242 = null;
         this._pos = savedPos42;
       }
-      var result242 = result243 !== null
+      var result241 = result242 !== null
         ? (function() { 
           return String.fromCharCode(parseInt("0x" + (arguments[1]) + (arguments[2])));
-         }).apply(this, result243)
+         }).apply(this, result242)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result242
+        result:  result241
       };
-      return result242;
+      return result241;
     },
     
     _parse_unicodeEscapeSequence: function(context) {
@@ -2493,57 +2474,57 @@ PEG.grammarParser = (function(){
       
       var savedPos43 = this._pos;
       if (this._input.substr(this._pos, 2) === "\\u") {
-        var result249 = "\\u";
+        var result248 = "\\u";
         this._pos += 2;
       } else {
-        var result249 = null;
+        var result248 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("\\u"));
         }
       }
-      if (result249 !== null) {
-        var result250 = this._parse_hexDigit(context);
-        if (result250 !== null) {
-          var result251 = this._parse_hexDigit(context);
-          if (result251 !== null) {
-            var result252 = this._parse_hexDigit(context);
-            if (result252 !== null) {
-              var result253 = this._parse_hexDigit(context);
-              if (result253 !== null) {
-                var result248 = [result249, result250, result251, result252, result253];
+      if (result248 !== null) {
+        var result249 = this._parse_hexDigit(context);
+        if (result249 !== null) {
+          var result250 = this._parse_hexDigit(context);
+          if (result250 !== null) {
+            var result251 = this._parse_hexDigit(context);
+            if (result251 !== null) {
+              var result252 = this._parse_hexDigit(context);
+              if (result252 !== null) {
+                var result247 = [result248, result249, result250, result251, result252];
               } else {
-                var result248 = null;
+                var result247 = null;
                 this._pos = savedPos43;
               }
             } else {
-              var result248 = null;
+              var result247 = null;
               this._pos = savedPos43;
             }
           } else {
-            var result248 = null;
+            var result247 = null;
             this._pos = savedPos43;
           }
         } else {
-          var result248 = null;
+          var result247 = null;
           this._pos = savedPos43;
         }
       } else {
-        var result248 = null;
+        var result247 = null;
         this._pos = savedPos43;
       }
-      var result247 = result248 !== null
+      var result246 = result247 !== null
         ? (function() { 
           return String.fromCharCode(parseInt("0x" + (arguments[1]) + (arguments[2]) + (arguments[3]) + (arguments[4])));
-         }).apply(this, result248)
+         }).apply(this, result247)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result247
+        result:  result246
       };
-      return result247;
+      return result246;
     },
     
     _parse_eolEscapeSequence: function(context) {
@@ -2559,37 +2540,37 @@ PEG.grammarParser = (function(){
       
       var savedPos44 = this._pos;
       if (this._input.substr(this._pos, 1) === "\\") {
-        var result256 = "\\";
+        var result255 = "\\";
         this._pos += 1;
       } else {
-        var result256 = null;
+        var result255 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("\\"));
         }
       }
-      if (result256 !== null) {
-        var result257 = this._parse_eol(context);
-        if (result257 !== null) {
-          var result255 = [result256, result257];
+      if (result255 !== null) {
+        var result256 = this._parse_eol(context);
+        if (result256 !== null) {
+          var result254 = [result255, result256];
         } else {
-          var result255 = null;
+          var result254 = null;
           this._pos = savedPos44;
         }
       } else {
-        var result255 = null;
+        var result254 = null;
         this._pos = savedPos44;
       }
-      var result254 = result255 !== null
-        ? (function() {  return (arguments[1]);  }).apply(this, result255)
+      var result253 = result254 !== null
+        ? (function() {  return (arguments[1]);  }).apply(this, result254)
         : null;
       
       
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result254
+        result:  result253
       };
-      return result254;
+      return result253;
     },
     
     _parse_digit: function(context) {
@@ -2604,10 +2585,10 @@ PEG.grammarParser = (function(){
       
       
       if (this._input.substr(this._pos).match(/^[0-9]/) !== null) {
-        var result258 = this._input.charAt(this._pos);
+        var result257 = this._input.charAt(this._pos);
         this._pos++;
       } else {
-        var result258 = null;
+        var result257 = null;
         if (context.reportMatchFailures) {
           this._matchFailed('[' + "0-9" + ']');
         }
@@ -2617,9 +2598,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result258
+        result:  result257
       };
-      return result258;
+      return result257;
     },
     
     _parse_hexDigit: function(context) {
@@ -2634,10 +2615,10 @@ PEG.grammarParser = (function(){
       
       
       if (this._input.substr(this._pos).match(/^[0-9a-fA-F]/) !== null) {
-        var result259 = this._input.charAt(this._pos);
+        var result258 = this._input.charAt(this._pos);
         this._pos++;
       } else {
-        var result259 = null;
+        var result258 = null;
         if (context.reportMatchFailures) {
           this._matchFailed('[' + "0-9a-fA-F" + ']');
         }
@@ -2647,9 +2628,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result259
+        result:  result258
       };
-      return result259;
+      return result258;
     },
     
     _parse_letter: function(context) {
@@ -2663,15 +2644,15 @@ PEG.grammarParser = (function(){
       var pos = this._pos;
       
       
-      var result262 = this._parse_lowerCaseLetter(context);
-      if (result262 !== null) {
-        var result260 = result262;
+      var result261 = this._parse_lowerCaseLetter(context);
+      if (result261 !== null) {
+        var result259 = result261;
       } else {
-        var result261 = this._parse_upperCaseLetter(context);
-        if (result261 !== null) {
-          var result260 = result261;
+        var result260 = this._parse_upperCaseLetter(context);
+        if (result260 !== null) {
+          var result259 = result260;
         } else {
-          var result260 = null;;
+          var result259 = null;;
         };
       }
       
@@ -2679,9 +2660,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result260
+        result:  result259
       };
-      return result260;
+      return result259;
     },
     
     _parse_lowerCaseLetter: function(context) {
@@ -2696,10 +2677,10 @@ PEG.grammarParser = (function(){
       
       
       if (this._input.substr(this._pos).match(/^[a-z]/) !== null) {
-        var result263 = this._input.charAt(this._pos);
+        var result262 = this._input.charAt(this._pos);
         this._pos++;
       } else {
-        var result263 = null;
+        var result262 = null;
         if (context.reportMatchFailures) {
           this._matchFailed('[' + "a-z" + ']');
         }
@@ -2709,9 +2690,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result263
+        result:  result262
       };
-      return result263;
+      return result262;
     },
     
     _parse_upperCaseLetter: function(context) {
@@ -2726,10 +2707,10 @@ PEG.grammarParser = (function(){
       
       
       if (this._input.substr(this._pos).match(/^[A-Z]/) !== null) {
-        var result264 = this._input.charAt(this._pos);
+        var result263 = this._input.charAt(this._pos);
         this._pos++;
       } else {
-        var result264 = null;
+        var result263 = null;
         if (context.reportMatchFailures) {
           this._matchFailed('[' + "A-Z" + ']');
         }
@@ -2739,9 +2720,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result264
+        result:  result263
       };
-      return result264;
+      return result263;
     },
     
     _parse___: function(context) {
@@ -2755,38 +2736,38 @@ PEG.grammarParser = (function(){
       var pos = this._pos;
       
       
-      var result265 = [];
-      var result269 = this._parse_whitespace(context);
-      if (result269 !== null) {
-        var result266 = result269;
+      var result264 = [];
+      var result268 = this._parse_whitespace(context);
+      if (result268 !== null) {
+        var result265 = result268;
       } else {
-        var result268 = this._parse_eol(context);
-        if (result268 !== null) {
-          var result266 = result268;
+        var result267 = this._parse_eol(context);
+        if (result267 !== null) {
+          var result265 = result267;
         } else {
-          var result267 = this._parse_comment(context);
-          if (result267 !== null) {
-            var result266 = result267;
+          var result266 = this._parse_comment(context);
+          if (result266 !== null) {
+            var result265 = result266;
           } else {
-            var result266 = null;;
+            var result265 = null;;
           };
         };
       }
-      while (result266 !== null) {
-        result265.push(result266);
-        var result269 = this._parse_whitespace(context);
-        if (result269 !== null) {
-          var result266 = result269;
+      while (result265 !== null) {
+        result264.push(result265);
+        var result268 = this._parse_whitespace(context);
+        if (result268 !== null) {
+          var result265 = result268;
         } else {
-          var result268 = this._parse_eol(context);
-          if (result268 !== null) {
-            var result266 = result268;
+          var result267 = this._parse_eol(context);
+          if (result267 !== null) {
+            var result265 = result267;
           } else {
-            var result267 = this._parse_comment(context);
-            if (result267 !== null) {
-              var result266 = result267;
+            var result266 = this._parse_comment(context);
+            if (result266 !== null) {
+              var result265 = result266;
             } else {
-              var result266 = null;;
+              var result265 = null;;
             };
           };
         }
@@ -2796,9 +2777,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result265
+        result:  result264
       };
-      return result265;
+      return result264;
     },
     
     _parse_comment: function(context) {
@@ -2813,27 +2794,27 @@ PEG.grammarParser = (function(){
       
       var savedReportMatchFailures = context.reportMatchFailures;
       context.reportMatchFailures = false;
-      var result272 = this._parse_singleLineComment(context);
-      if (result272 !== null) {
-        var result270 = result272;
+      var result271 = this._parse_singleLineComment(context);
+      if (result271 !== null) {
+        var result269 = result271;
       } else {
-        var result271 = this._parse_multiLineComment(context);
-        if (result271 !== null) {
-          var result270 = result271;
+        var result270 = this._parse_multiLineComment(context);
+        if (result270 !== null) {
+          var result269 = result270;
         } else {
-          var result270 = null;;
+          var result269 = null;;
         };
       }
       context.reportMatchFailures = savedReportMatchFailures;
-      if (context.reportMatchFailures && result270 === null) {
+      if (context.reportMatchFailures && result269 === null) {
         this._matchFailed("comment");
       }
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result270
+        result:  result269
       };
-      return result270;
+      return result269;
     },
     
     _parse_singleLineComment: function(context) {
@@ -2849,91 +2830,91 @@ PEG.grammarParser = (function(){
       
       var savedPos45 = this._pos;
       if (this._input.substr(this._pos, 2) === "//") {
-        var result274 = "//";
+        var result273 = "//";
         this._pos += 2;
       } else {
-        var result274 = null;
+        var result273 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("//"));
         }
       }
-      if (result274 !== null) {
-        var result275 = [];
+      if (result273 !== null) {
+        var result274 = [];
         var savedPos46 = this._pos;
         var savedPos47 = this._pos;
         var savedReportMatchFailuresVar6 = context.reportMatchFailures;
         context.reportMatchFailures = false;
-        var result279 = this._parse_eolChar(context);
+        var result278 = this._parse_eolChar(context);
         context.reportMatchFailures = savedReportMatchFailuresVar6;
-        if (result279 === null) {
-          var result277 = '';
+        if (result278 === null) {
+          var result276 = '';
         } else {
-          var result277 = null;
+          var result276 = null;
           this._pos = savedPos47;
         }
-        if (result277 !== null) {
+        if (result276 !== null) {
           if (this._input.length > this._pos) {
-            var result278 = this._input.charAt(this._pos);
+            var result277 = this._input.charAt(this._pos);
             this._pos++;
           } else {
-            var result278 = null;
+            var result277 = null;
             if (context.reportMatchFailures) {
               this._matchFailed('any character');
             }
           }
-          if (result278 !== null) {
-            var result276 = [result277, result278];
+          if (result277 !== null) {
+            var result275 = [result276, result277];
           } else {
-            var result276 = null;
+            var result275 = null;
             this._pos = savedPos46;
           }
         } else {
-          var result276 = null;
+          var result275 = null;
           this._pos = savedPos46;
         }
-        while (result276 !== null) {
-          result275.push(result276);
+        while (result275 !== null) {
+          result274.push(result275);
           var savedPos46 = this._pos;
           var savedPos47 = this._pos;
           var savedReportMatchFailuresVar6 = context.reportMatchFailures;
           context.reportMatchFailures = false;
-          var result279 = this._parse_eolChar(context);
+          var result278 = this._parse_eolChar(context);
           context.reportMatchFailures = savedReportMatchFailuresVar6;
-          if (result279 === null) {
-            var result277 = '';
+          if (result278 === null) {
+            var result276 = '';
           } else {
-            var result277 = null;
+            var result276 = null;
             this._pos = savedPos47;
           }
-          if (result277 !== null) {
+          if (result276 !== null) {
             if (this._input.length > this._pos) {
-              var result278 = this._input.charAt(this._pos);
+              var result277 = this._input.charAt(this._pos);
               this._pos++;
             } else {
-              var result278 = null;
+              var result277 = null;
               if (context.reportMatchFailures) {
                 this._matchFailed('any character');
               }
             }
-            if (result278 !== null) {
-              var result276 = [result277, result278];
+            if (result277 !== null) {
+              var result275 = [result276, result277];
             } else {
-              var result276 = null;
+              var result275 = null;
               this._pos = savedPos46;
             }
           } else {
-            var result276 = null;
+            var result275 = null;
             this._pos = savedPos46;
           }
         }
-        if (result275 !== null) {
-          var result273 = [result274, result275];
+        if (result274 !== null) {
+          var result272 = [result273, result274];
         } else {
-          var result273 = null;
+          var result272 = null;
           this._pos = savedPos45;
         }
       } else {
-        var result273 = null;
+        var result272 = null;
         this._pos = savedPos45;
       }
       
@@ -2941,9 +2922,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result273
+        result:  result272
       };
-      return result273;
+      return result272;
     },
     
     _parse_multiLineComment: function(context) {
@@ -2959,121 +2940,121 @@ PEG.grammarParser = (function(){
       
       var savedPos48 = this._pos;
       if (this._input.substr(this._pos, 2) === "/*") {
-        var result281 = "/*";
+        var result280 = "/*";
         this._pos += 2;
       } else {
-        var result281 = null;
+        var result280 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("/*"));
         }
       }
-      if (result281 !== null) {
-        var result282 = [];
+      if (result280 !== null) {
+        var result281 = [];
         var savedPos49 = this._pos;
         var savedPos50 = this._pos;
         var savedReportMatchFailuresVar7 = context.reportMatchFailures;
         context.reportMatchFailures = false;
         if (this._input.substr(this._pos, 2) === "*/") {
-          var result287 = "*/";
+          var result286 = "*/";
           this._pos += 2;
         } else {
-          var result287 = null;
+          var result286 = null;
           if (context.reportMatchFailures) {
             this._matchFailed(this._quoteString("*/"));
           }
         }
         context.reportMatchFailures = savedReportMatchFailuresVar7;
-        if (result287 === null) {
-          var result285 = '';
+        if (result286 === null) {
+          var result284 = '';
         } else {
-          var result285 = null;
+          var result284 = null;
           this._pos = savedPos50;
         }
-        if (result285 !== null) {
+        if (result284 !== null) {
           if (this._input.length > this._pos) {
-            var result286 = this._input.charAt(this._pos);
+            var result285 = this._input.charAt(this._pos);
             this._pos++;
           } else {
-            var result286 = null;
+            var result285 = null;
             if (context.reportMatchFailures) {
               this._matchFailed('any character');
             }
           }
-          if (result286 !== null) {
-            var result284 = [result285, result286];
+          if (result285 !== null) {
+            var result283 = [result284, result285];
           } else {
-            var result284 = null;
+            var result283 = null;
             this._pos = savedPos49;
           }
         } else {
-          var result284 = null;
+          var result283 = null;
           this._pos = savedPos49;
         }
-        while (result284 !== null) {
-          result282.push(result284);
+        while (result283 !== null) {
+          result281.push(result283);
           var savedPos49 = this._pos;
           var savedPos50 = this._pos;
           var savedReportMatchFailuresVar7 = context.reportMatchFailures;
           context.reportMatchFailures = false;
           if (this._input.substr(this._pos, 2) === "*/") {
-            var result287 = "*/";
+            var result286 = "*/";
             this._pos += 2;
           } else {
-            var result287 = null;
+            var result286 = null;
             if (context.reportMatchFailures) {
               this._matchFailed(this._quoteString("*/"));
             }
           }
           context.reportMatchFailures = savedReportMatchFailuresVar7;
-          if (result287 === null) {
-            var result285 = '';
+          if (result286 === null) {
+            var result284 = '';
           } else {
-            var result285 = null;
+            var result284 = null;
             this._pos = savedPos50;
           }
-          if (result285 !== null) {
+          if (result284 !== null) {
             if (this._input.length > this._pos) {
-              var result286 = this._input.charAt(this._pos);
+              var result285 = this._input.charAt(this._pos);
               this._pos++;
             } else {
-              var result286 = null;
+              var result285 = null;
               if (context.reportMatchFailures) {
                 this._matchFailed('any character');
               }
             }
-            if (result286 !== null) {
-              var result284 = [result285, result286];
+            if (result285 !== null) {
+              var result283 = [result284, result285];
             } else {
-              var result284 = null;
+              var result283 = null;
               this._pos = savedPos49;
             }
           } else {
-            var result284 = null;
+            var result283 = null;
             this._pos = savedPos49;
           }
         }
-        if (result282 !== null) {
+        if (result281 !== null) {
           if (this._input.substr(this._pos, 2) === "*/") {
-            var result283 = "*/";
+            var result282 = "*/";
             this._pos += 2;
           } else {
-            var result283 = null;
+            var result282 = null;
             if (context.reportMatchFailures) {
               this._matchFailed(this._quoteString("*/"));
             }
           }
-          if (result283 !== null) {
-            var result280 = [result281, result282, result283];
+          if (result282 !== null) {
+            var result279 = [result280, result281, result282];
           } else {
-            var result280 = null;
+            var result279 = null;
             this._pos = savedPos48;
           }
         } else {
-          var result280 = null;
+          var result279 = null;
           this._pos = savedPos48;
         }
       } else {
-        var result280 = null;
+        var result279 = null;
         this._pos = savedPos48;
       }
       
@@ -3081,9 +3062,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result280
+        result:  result279
       };
-      return result280;
+      return result279;
     },
     
     _parse_eol: function(context) {
@@ -3099,81 +3080,81 @@ PEG.grammarParser = (function(){
       var savedReportMatchFailures = context.reportMatchFailures;
       context.reportMatchFailures = false;
       if (this._input.substr(this._pos, 1) === "\n") {
-        var result293 = "\n";
+        var result292 = "\n";
         this._pos += 1;
       } else {
-        var result293 = null;
+        var result292 = null;
         if (context.reportMatchFailures) {
           this._matchFailed(this._quoteString("\n"));
         }
       }
-      if (result293 !== null) {
-        var result288 = result293;
+      if (result292 !== null) {
+        var result287 = result292;
       } else {
         if (this._input.substr(this._pos, 2) === "\r\n") {
-          var result292 = "\r\n";
+          var result291 = "\r\n";
           this._pos += 2;
         } else {
-          var result292 = null;
+          var result291 = null;
           if (context.reportMatchFailures) {
             this._matchFailed(this._quoteString("\r\n"));
           }
         }
-        if (result292 !== null) {
-          var result288 = result292;
+        if (result291 !== null) {
+          var result287 = result291;
         } else {
           if (this._input.substr(this._pos, 1) === "\r") {
-            var result291 = "\r";
+            var result290 = "\r";
             this._pos += 1;
           } else {
-            var result291 = null;
+            var result290 = null;
             if (context.reportMatchFailures) {
               this._matchFailed(this._quoteString("\r"));
             }
           }
-          if (result291 !== null) {
-            var result288 = result291;
+          if (result290 !== null) {
+            var result287 = result290;
           } else {
             if (this._input.substr(this._pos, 1) === "\u2028") {
-              var result290 = "\u2028";
+              var result289 = "\u2028";
               this._pos += 1;
             } else {
-              var result290 = null;
+              var result289 = null;
               if (context.reportMatchFailures) {
                 this._matchFailed(this._quoteString("\u2028"));
               }
             }
-            if (result290 !== null) {
-              var result288 = result290;
+            if (result289 !== null) {
+              var result287 = result289;
             } else {
               if (this._input.substr(this._pos, 1) === "\u2029") {
-                var result289 = "\u2029";
+                var result288 = "\u2029";
                 this._pos += 1;
               } else {
-                var result289 = null;
+                var result288 = null;
                 if (context.reportMatchFailures) {
                   this._matchFailed(this._quoteString("\u2029"));
                 }
               }
-              if (result289 !== null) {
-                var result288 = result289;
+              if (result288 !== null) {
+                var result287 = result288;
               } else {
-                var result288 = null;;
+                var result287 = null;;
               };
             };
           };
         };
       }
       context.reportMatchFailures = savedReportMatchFailures;
-      if (context.reportMatchFailures && result288 === null) {
+      if (context.reportMatchFailures && result287 === null) {
         this._matchFailed("end of line");
       }
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result288
+        result:  result287
       };
-      return result288;
+      return result287;
     },
     
     _parse_eolChar: function(context) {
@@ -3188,10 +3169,10 @@ PEG.grammarParser = (function(){
       
       
       if (this._input.substr(this._pos).match(/^[\n\r\u2028\u2029]/) !== null) {
-        var result294 = this._input.charAt(this._pos);
+        var result293 = this._input.charAt(this._pos);
         this._pos++;
       } else {
-        var result294 = null;
+        var result293 = null;
         if (context.reportMatchFailures) {
           this._matchFailed('[' + "\\n\\r\\u2028\\u2029" + ']');
         }
@@ -3201,9 +3182,9 @@ PEG.grammarParser = (function(){
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result294
+        result:  result293
       };
-      return result294;
+      return result293;
     },
     
     _parse_whitespace: function(context) {
@@ -3219,24 +3200,24 @@ PEG.grammarParser = (function(){
       var savedReportMatchFailures = context.reportMatchFailures;
       context.reportMatchFailures = false;
       if (this._input.substr(this._pos).match(/^[ 	  ᠎ -   　]/) !== null) {
-        var result295 = this._input.charAt(this._pos);
+        var result294 = this._input.charAt(this._pos);
         this._pos++;
       } else {
-        var result295 = null;
+        var result294 = null;
         if (context.reportMatchFailures) {
           this._matchFailed('[' + " 	  ᠎ -   　" + ']');
         }
       }
       context.reportMatchFailures = savedReportMatchFailures;
-      if (context.reportMatchFailures && result295 === null) {
+      if (context.reportMatchFailures && result294 === null) {
         this._matchFailed("whitespace");
       }
       
       this._cache[cacheKey] = {
         nextPos: this._pos,
-        result:  result295
+        result:  result294
       };
-      return result295;
+      return result294;
     },
     
     /*
diff --git a/lib/metagrammar.pegjs b/lib/metagrammar.pegjs
index 2d355cf..82acfed 100644
--- a/lib/metagrammar.pegjs
+++ b/lib/metagrammar.pegjs
@@ -34,11 +34,9 @@ prefixed
   / suffixed
 
 suffixed
-  : primary question {
-      return new PEG.Grammar.Choice([$1, new PEG.Grammar.Literal("")]);
-    }
-  / primary star { return new PEG.Grammar.ZeroOrMore($1); }
-  / primary plus { return new PEG.Grammar.OneOrMore($1);  }
+  : primary question { return new PEG.Grammar.Optional($1);   }
+  / primary star     { return new PEG.Grammar.ZeroOrMore($1); }
+  / primary plus     { return new PEG.Grammar.OneOrMore($1);  }
   / primary
 
 primary
diff --git a/test/compiler-test.js b/test/compiler-test.js
index 7cd8558..fb4899a 100644
--- a/test/compiler-test.js
+++ b/test/compiler-test.js
@@ -191,6 +191,7 @@ test("buildParser reports missing referenced rules", function() {
     'start: "a" "b" missing',
     'start: missing / "a" / "b"',
     'start: "a" / "b" / missing',
+    'start: missing?',
     'start: missing*',
     'start: missing+',
     'start: &missing',
@@ -214,6 +215,7 @@ test("buildParser reports left recursion", function() {
     'start: start "a" "b"',
     'start: start / "a" / "b"',
     'start: "a" / "b" / start',
+    'start: start?',
     'start: start*',
     'start: start+',
     'start: &start',
diff --git a/test/metagrammar-test.js b/test/metagrammar-test.js
index 293f675..e73d159 100644
--- a/test/metagrammar-test.js
+++ b/test/metagrammar-test.js
@@ -17,12 +17,11 @@ global.grammarParserDoesNotParse = function(input) {
 module("Grammar Parser");
 
 with (PEG.Grammar) {
-  var literalEmpty = new Literal("");
   var literalAbcd  = new Literal("abcd");
   var literalEfgh  = new Literal("efgh");
   var literalIjkl  = new Literal("ijkl");
 
-  var choice = new Choice([literalAbcd, literalEmpty]);
+  var choice = new Optional(literalAbcd);
 
   var notAbcd = new NotPredicate(literalAbcd);
   var notEfgh = new NotPredicate(literalEfgh);