diff --git a/lib/compiler.js b/lib/compiler.js
index 830add9..485510b 100644
--- a/lib/compiler.js
+++ b/lib/compiler.js
@@ -6,6 +6,8 @@
 
 (function() {
 
+function nop() {}
+
 /* ===== PEG ===== */
 
 /*
@@ -111,11 +113,11 @@ PEG.Grammar.Rule.prototype.checkReferencedRulesExist = function(grammar) {
   this._expression.checkReferencedRulesExist(grammar);
 };
 
-PEG.Grammar.Literal.prototype.checkReferencedRulesExist = function(grammar) {};
+PEG.Grammar.Literal.prototype.checkReferencedRulesExist = nop;
 
-PEG.Grammar.Class.prototype.checkReferencedRulesExist = function(grammar) {};
+PEG.Grammar.Class.prototype.checkReferencedRulesExist = nop;
 
-PEG.Grammar.Any.prototype.checkReferencedRulesExist = function(grammar) {};
+PEG.Grammar.Any.prototype.checkReferencedRulesExist = nop;
 
 PEG.Grammar.Sequence.prototype.checkReferencedRulesExist = function(grammar) {
   PEG.ArrayUtils.each(this._elements, function(element) {
@@ -153,11 +155,11 @@ PEG.Grammar.Rule.prototype.checkNoLeftRecursion = function(grammar, appliedRules
   this._expression.checkNoLeftRecursion(grammar, appliedRules.concat(this._name));
 };
 
-PEG.Grammar.Literal.prototype.checkNoLeftRecursion = function(grammar, appliedRules) {};
+PEG.Grammar.Literal.prototype.checkNoLeftRecursion = nop;
 
-PEG.Grammar.Class.prototype.checkNoLeftRecursion = function(grammar, appliedRules) {};
+PEG.Grammar.Class.prototype.checkNoLeftRecursion = nop;
 
-PEG.Grammar.Any.prototype.checkNoLeftRecursion = function(grammar, appliedRules) {};
+PEG.Grammar.Any.prototype.checkNoLeftRecursion = nop;
 
 PEG.Grammar.Sequence.prototype.checkNoLeftRecursion = function(grammar, appliedRules) {
   if (this._elements.length > 0) {