diff --git a/lib/parser.js b/lib/parser.js
index a86badc..e7d8c0f 100644
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -149,18 +149,15 @@ module.exports = (function() {
                 expression: expression
               };
             },
-        peg$c36 = void 0,
-        peg$c37 = function(name) {
-              return {
-                type: "rule_ref",
-                name: name
-              };
+        peg$c36 = "(",
+        peg$c37 = { type: "literal", value: "(", description: "\"(\"" },
+        peg$c38 = ")",
+        peg$c39 = { type: "literal", value: ")", description: "\")\"" },
+        peg$c40 = function(expression) { return expression; },
+        peg$c41 = void 0,
+        peg$c42 = function(name) {
+              return { type: "rule_ref", name: name }
             },
-        peg$c38 = "(",
-        peg$c39 = { type: "literal", value: "(", description: "\"(\"" },
-        peg$c40 = ")",
-        peg$c41 = { type: "literal", value: ")", description: "\")\"" },
-        peg$c42 = function(expression) { return expression; },
         peg$c43 = { type: "any", description: "any character" },
         peg$c44 = { type: "other", description: "whitespace" },
         peg$c45 = "\t",
@@ -1234,6 +1231,71 @@ module.exports = (function() {
     }
 
     function peg$parsePrimaryExpression() {
+      var s0, s1, s2, s3, s4, s5;
+
+      s0 = peg$parseLiteralMatcher();
+      if (s0 === peg$FAILED) {
+        s0 = peg$parseCharacterClassMatcher();
+        if (s0 === peg$FAILED) {
+          s0 = peg$parseAnyMatcher();
+          if (s0 === peg$FAILED) {
+            s0 = peg$parseRuleReferenceExpression();
+            if (s0 === peg$FAILED) {
+              s0 = peg$currPos;
+              if (input.charCodeAt(peg$currPos) === 40) {
+                s1 = peg$c36;
+                peg$currPos++;
+              } else {
+                s1 = peg$FAILED;
+                if (peg$silentFails === 0) { peg$fail(peg$c37); }
+              }
+              if (s1 !== peg$FAILED) {
+                s2 = peg$parse__();
+                if (s2 !== peg$FAILED) {
+                  s3 = peg$parseChoiceExpression();
+                  if (s3 !== peg$FAILED) {
+                    s4 = peg$parse__();
+                    if (s4 !== peg$FAILED) {
+                      if (input.charCodeAt(peg$currPos) === 41) {
+                        s5 = peg$c38;
+                        peg$currPos++;
+                      } else {
+                        s5 = peg$FAILED;
+                        if (peg$silentFails === 0) { peg$fail(peg$c39); }
+                      }
+                      if (s5 !== peg$FAILED) {
+                        peg$reportedPos = s0;
+                        s1 = peg$c40(s3);
+                        s0 = s1;
+                      } else {
+                        peg$currPos = s0;
+                        s0 = peg$c0;
+                      }
+                    } else {
+                      peg$currPos = s0;
+                      s0 = peg$c0;
+                    }
+                  } else {
+                    peg$currPos = s0;
+                    s0 = peg$c0;
+                  }
+                } else {
+                  peg$currPos = s0;
+                  s0 = peg$c0;
+                }
+              } else {
+                peg$currPos = s0;
+                s0 = peg$c0;
+              }
+            }
+          }
+        }
+      }
+
+      return s0;
+    }
+
+    function peg$parseRuleReferenceExpression() {
       var s0, s1, s2, s3, s4, s5, s6, s7;
 
       s0 = peg$currPos;
@@ -1287,14 +1349,14 @@ module.exports = (function() {
         }
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
         }
         if (s2 !== peg$FAILED) {
           peg$reportedPos = s0;
-          s1 = peg$c37(s1);
+          s1 = peg$c42(s1);
           s0 = s1;
         } else {
           peg$currPos = s0;
@@ -1304,63 +1366,6 @@ module.exports = (function() {
         peg$currPos = s0;
         s0 = peg$c0;
       }
-      if (s0 === peg$FAILED) {
-        s0 = peg$parseLiteralMatcher();
-        if (s0 === peg$FAILED) {
-          s0 = peg$parseCharacterClassMatcher();
-          if (s0 === peg$FAILED) {
-            s0 = peg$parseAnyMatcher();
-            if (s0 === peg$FAILED) {
-              s0 = peg$currPos;
-              if (input.charCodeAt(peg$currPos) === 40) {
-                s1 = peg$c38;
-                peg$currPos++;
-              } else {
-                s1 = peg$FAILED;
-                if (peg$silentFails === 0) { peg$fail(peg$c39); }
-              }
-              if (s1 !== peg$FAILED) {
-                s2 = peg$parse__();
-                if (s2 !== peg$FAILED) {
-                  s3 = peg$parseChoiceExpression();
-                  if (s3 !== peg$FAILED) {
-                    s4 = peg$parse__();
-                    if (s4 !== peg$FAILED) {
-                      if (input.charCodeAt(peg$currPos) === 41) {
-                        s5 = peg$c40;
-                        peg$currPos++;
-                      } else {
-                        s5 = peg$FAILED;
-                        if (peg$silentFails === 0) { peg$fail(peg$c41); }
-                      }
-                      if (s5 !== peg$FAILED) {
-                        peg$reportedPos = s0;
-                        s1 = peg$c42(s3);
-                        s0 = s1;
-                      } else {
-                        peg$currPos = s0;
-                        s0 = peg$c0;
-                      }
-                    } else {
-                      peg$currPos = s0;
-                      s0 = peg$c0;
-                    }
-                  } else {
-                    peg$currPos = s0;
-                    s0 = peg$c0;
-                  }
-                } else {
-                  peg$currPos = s0;
-                  s0 = peg$c0;
-                }
-              } else {
-                peg$currPos = s0;
-                s0 = peg$c0;
-              }
-            }
-          }
-        }
-      }
 
       return s0;
     }
@@ -1559,7 +1564,7 @@ module.exports = (function() {
         }
         peg$silentFails--;
         if (s5 === peg$FAILED) {
-          s4 = peg$c36;
+          s4 = peg$c41;
         } else {
           peg$currPos = s4;
           s4 = peg$c0;
@@ -1591,7 +1596,7 @@ module.exports = (function() {
           }
           peg$silentFails--;
           if (s5 === peg$FAILED) {
-            s4 = peg$c36;
+            s4 = peg$c41;
           } else {
             peg$currPos = s4;
             s4 = peg$c0;
@@ -1665,7 +1670,7 @@ module.exports = (function() {
         }
         peg$silentFails--;
         if (s5 === peg$FAILED) {
-          s4 = peg$c36;
+          s4 = peg$c41;
         } else {
           peg$currPos = s4;
           s4 = peg$c0;
@@ -1700,7 +1705,7 @@ module.exports = (function() {
           }
           peg$silentFails--;
           if (s5 === peg$FAILED) {
-            s4 = peg$c36;
+            s4 = peg$c41;
           } else {
             peg$currPos = s4;
             s4 = peg$c0;
@@ -1765,7 +1770,7 @@ module.exports = (function() {
         s5 = peg$parseLineTerminator();
         peg$silentFails--;
         if (s5 === peg$FAILED) {
-          s4 = peg$c36;
+          s4 = peg$c41;
         } else {
           peg$currPos = s4;
           s4 = peg$c0;
@@ -1791,7 +1796,7 @@ module.exports = (function() {
           s5 = peg$parseLineTerminator();
           peg$silentFails--;
           if (s5 === peg$FAILED) {
-            s4 = peg$c36;
+            s4 = peg$c41;
           } else {
             peg$currPos = s4;
             s4 = peg$c0;
@@ -1834,7 +1839,7 @@ module.exports = (function() {
       s2 = peg$parseReservedWord();
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c36;
+        s1 = peg$c41;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -2314,7 +2319,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c36;
+        s1 = peg$c41;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -2391,7 +2396,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c36;
+        s1 = peg$c41;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -2591,7 +2596,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c36;
+        s1 = peg$c41;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -2689,7 +2694,7 @@ module.exports = (function() {
           s3 = peg$parseDecimalDigit();
           peg$silentFails--;
           if (s3 === peg$FAILED) {
-            s2 = peg$c36;
+            s2 = peg$c41;
           } else {
             peg$currPos = s2;
             s2 = peg$c0;
@@ -2862,7 +2867,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s2 === peg$FAILED) {
-        s1 = peg$c36;
+        s1 = peg$c41;
       } else {
         peg$currPos = s1;
         s1 = peg$c0;
@@ -3388,7 +3393,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3425,7 +3430,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3462,7 +3467,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3499,7 +3504,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3536,7 +3541,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3573,7 +3578,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3610,7 +3615,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3647,7 +3652,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3684,7 +3689,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3721,7 +3726,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3758,7 +3763,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3795,7 +3800,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3832,7 +3837,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3869,7 +3874,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3906,7 +3911,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3943,7 +3948,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -3980,7 +3985,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4017,7 +4022,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4054,7 +4059,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4091,7 +4096,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4128,7 +4133,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4165,7 +4170,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4202,7 +4207,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4239,7 +4244,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4276,7 +4281,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4313,7 +4318,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4350,7 +4355,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4387,7 +4392,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4424,7 +4429,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4461,7 +4466,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4498,7 +4503,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4535,7 +4540,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4572,7 +4577,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4609,7 +4614,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4646,7 +4651,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4683,7 +4688,7 @@ module.exports = (function() {
         s3 = peg$parseIdentifierPart();
         peg$silentFails--;
         if (s3 === peg$FAILED) {
-          s2 = peg$c36;
+          s2 = peg$c41;
         } else {
           peg$currPos = s2;
           s2 = peg$c0;
@@ -4832,7 +4837,7 @@ module.exports = (function() {
       }
       peg$silentFails--;
       if (s1 === peg$FAILED) {
-        s0 = peg$c36;
+        s0 = peg$c41;
       } else {
         peg$currPos = s0;
         s0 = peg$c0;
diff --git a/spec/parser.spec.js b/spec/parser.spec.js
index 0561845..f484374 100644
--- a/spec/parser.spec.js
+++ b/spec/parser.spec.js
@@ -318,15 +318,20 @@ describe("PEG.js grammar parser", function() {
 
   /* Canonical PrimaryExpression is "\"abcd\"". */
   it("parses PrimaryExpression", function() {
-    expect('start = a'         ).toParseAs(ruleRefGrammar("a"));
     expect('start = "abcd"'    ).toParseAs(literalGrammar("abcd"));
     expect('start = [a-d]'     ).toParseAs(classGrammar([["a", "d"]], "[a-d]"));
     expect('start = .'         ).toParseAs(oneRuleGrammar({ type: "any" }));
+    expect('start = a'         ).toParseAs(ruleRefGrammar("a"));
     expect('start = ("abcd")'  ).toParseAs(literalGrammar("abcd"));
     expect('start = (\n"abcd")').toParseAs(literalGrammar("abcd"));
     expect('start = ("abcd"\n)').toParseAs(literalGrammar("abcd"));
   });
 
+  /* Canonical RuleReferenceExpression is "\"abcd\"". */
+  it("parses RuleReferenceExpression", function() {
+    expect('start = a').toParseAs(ruleRefGrammar("a"));
+  });
+
   /* The SourceCharacter rule is not tested. */
 
   /* Canonical WhiteSpace is " ". */
diff --git a/src/parser.pegjs b/src/parser.pegjs
index 0ae36fc..4eb872a 100644
--- a/src/parser.pegjs
+++ b/src/parser.pegjs
@@ -155,17 +155,17 @@ SuffixedExpression
   / PrimaryExpression
 
 PrimaryExpression
-  = name:IdentifierName !(__ (StringLiteral __)? "=") {
-      return {
-        type: "rule_ref",
-        name: name
-      };
-    }
-  / LiteralMatcher
+  = LiteralMatcher
   / CharacterClassMatcher
   / AnyMatcher
+  / RuleReferenceExpression
   / "(" __ expression:Expression __ ")" { return expression; }
 
+RuleReferenceExpression
+  = name:IdentifierName !(__ (StringLiteral __)? "=") {
+      return { type: "rule_ref", name: name }
+    }
+
 /* "Lexical" elements */
 
 SourceCharacter