diff --git a/lib/compiler.js b/lib/compiler.js
index 84865b0..678fd3c 100644
--- a/lib/compiler.js
+++ b/lib/compiler.js
@@ -56,6 +56,24 @@ PEG.buildParser = function(grammar, startRule) {
 /* Array manipulation utility functions. */
 
 PEG.ArrayUtils = {
+  /*
+   * The code needs to be in sync with a code template in
+   * PEG.Grammar.Action.prototype.compile.
+   */
+  contains: function(array, value) {
+    /*
+     * Stupid IE does not have Array.prototype.indexOf, otherwise this function
+     * would be a one-liner.
+     */
+    var length = array.length;
+    for (var i = 0; i < length; i++) {
+      if (array[i] === value) {
+        return true;
+      }
+    }
+    return false;
+  },
+
   each: function(array, callback) {
     var length = array.length;
     for (var i = 0; i < length; i++) {
@@ -289,7 +307,7 @@ PEG.Grammar.extendNodes("checkNoLeftRecursion", {
 
   RuleRef:
     function(grammar, appliedRules) {
-      if (appliedRules.indexOf(this._name) !== -1) {
+      if (PEG.ArrayUtils.contains(appliedRules, this._name)) {
         throw new PEG.Grammar.GrammarError("Left recursion detected for rule \"" + this._name + "\".");
       }
       grammar[this._name].checkNoLeftRecursion(grammar, appliedRules);
@@ -443,13 +461,28 @@ PEG.Compiler = {
       "        + '\"';",
       "    },",
       "    ",
+      /* This needs to be in sync with PEG.ArrayUtils.contains. */
+      "    _arrayContains: function(array, value) {",
+      "      /*",
+      "       * Stupid IE does not have Array.prototype.indexOf, otherwise this function",
+      "       * would be a one-liner.",
+      "       */",
+      "      var length = array.length;",
+      "      for (var i = 0; i < length; i++) {",
+      "        if (array[i] === value) {",
+      "          return true;",
+      "        }",
+      "      }",
+      "      return false;",
+      "    },",
+      "    ",
       "    _matchFailed: function(failure) {",
       "      if (this._pos > this._rightmostMatchFailuresPos) {",
       "        this._rightmostMatchFailuresPos = this._pos;",
       "        this._rightmostMatchFailuresExpected = [];",
       "      }",
       "      ",
-      "      if (this._rightmostMatchFailuresExpected.indexOf(failure) === -1) {",
+      "      if (!this._arrayContains(this._rightmostMatchFailuresExpected, failure)) {",
       "        this._rightmostMatchFailuresExpected.push(failure);",
       "      }",
       "    },",
diff --git a/lib/metagrammar.js b/lib/metagrammar.js
index 4a2a051..53f9095 100644
--- a/lib/metagrammar.js
+++ b/lib/metagrammar.js
@@ -19,13 +19,27 @@ PEG.grammarParser = (function(){
         + '"';
     },
     
+    _arrayContains: function(array, value) {
+      /*
+       * Stupid IE does not have Array.prototype.indexOf, otherwise this function
+       * would be a one-liner.
+       */
+      var length = array.length;
+      for (var i = 0; i < length; i++) {
+        if (array[i] === value) {
+          return true;
+        }
+      }
+      return false;
+    },
+    
     _matchFailed: function(failure) {
       if (this._pos > this._rightmostMatchFailuresPos) {
         this._rightmostMatchFailuresPos = this._pos;
         this._rightmostMatchFailuresExpected = [];
       }
       
-      if (this._rightmostMatchFailuresExpected.indexOf(failure) === -1) {
+      if (!this._arrayContains(this._rightmostMatchFailuresExpected, failure)) {
         this._rightmostMatchFailuresExpected.push(failure);
       }
     },
diff --git a/test/compiler-test.js b/test/compiler-test.js
index c4c9b7f..cd7fbd7 100644
--- a/test/compiler-test.js
+++ b/test/compiler-test.js
@@ -61,6 +61,16 @@ global.doesNotParseWithPos = function(parser, input, line, column) {
 
 module("PEG.ArrayUtils");
 
+test("contains", function() {
+  ok(!PEG.ArrayUtils.contains([], 42));
+
+  ok(PEG.ArrayUtils.contains([1, 2, 3], 1));
+  ok(PEG.ArrayUtils.contains([1, 2, 3], 2));
+  ok(PEG.ArrayUtils.contains([1, 2, 3], 3));
+  ok(!PEG.ArrayUtils.contains([1, 2, 3], 42));
+  ok(!PEG.ArrayUtils.contains([1, 2, 3], "2")); // Does it use |===|?
+});
+
 test("each", function() {
   var sum;
   function increment(x) { sum += x; }