diff --git a/bin/pegjs b/bin/pegjs
index 1807da2..6ea1ec1 100755
--- a/bin/pegjs
+++ b/bin/pegjs
@@ -5,7 +5,6 @@
 var fs      = require("fs");
 var path    = require("path");
 var peg     = require("../lib/peg");
-var objects = require("../lib/utils/objects");
 
 /* Helpers */
 
@@ -256,7 +255,7 @@ while (args.length > 0 && isOption(args[0])) {
   nextArg();
 }
 
-if (objects.keys(options.dependencies).length > 0) {
+if (Object.keys(options.dependencies).length > 0) {
   if (options.format !== "amd" && options.format !== "commonjs" && options.format !== "umd") {
       abort("Can't use the -d/--dependency option with the \"" + options.format + "\" module format.");
   }
diff --git a/lib/compiler/passes/generate-bytecode.js b/lib/compiler/passes/generate-bytecode.js
index bef6284..7bf673e 100644
--- a/lib/compiler/passes/generate-bytecode.js
+++ b/lib/compiler/passes/generate-bytecode.js
@@ -254,7 +254,7 @@ function generateBytecode(ast) {
   }
 
   function buildSemanticPredicate(code, negative, context) {
-    var functionIndex = addFunctionConst(objects.keys(context.env), code);
+    var functionIndex = addFunctionConst(Object.keys(context.env), code);
 
     return buildSequence(
       [op.UPDATE_SAVED_POS],
@@ -347,7 +347,7 @@ function generateBytecode(ast) {
             env:    env,
             action: node
           }),
-          functionIndex  = addFunctionConst(objects.keys(env), node.code);
+          functionIndex  = addFunctionConst(Object.keys(env), node.code);
 
       return emitCall
         ? buildSequence(
@@ -396,7 +396,7 @@ function generateBytecode(ast) {
         } else {
           if (context.action) {
             functionIndex = addFunctionConst(
-              objects.keys(context.env),
+              Object.keys(context.env),
               context.action.code
             );
 
diff --git a/lib/compiler/passes/generate-js.js b/lib/compiler/passes/generate-js.js
index feb6994..5f34c29 100644
--- a/lib/compiler/passes/generate-js.js
+++ b/lib/compiler/passes/generate-js.js
@@ -1260,7 +1260,7 @@ function generateJS(ast, options) {
 
       commonjs: function() {
         var parts          = [],
-            dependencyVars = objects.keys(options.dependencies),
+            dependencyVars = Object.keys(options.dependencies),
             requires       = dependencyVars.map(
               function(variable) {
                 return variable
@@ -1294,7 +1294,7 @@ function generateJS(ast, options) {
 
       amd: function() {
         var dependencyIds  = objects.values(options.dependencies),
-            dependencyVars = objects.keys(options.dependencies),
+            dependencyVars = Object.keys(options.dependencies),
             dependencies   = '['
               + dependencyIds.map(
                   function(id) { return '"' + js.stringEscape(id) + '"'; }
@@ -1332,7 +1332,7 @@ function generateJS(ast, options) {
       umd: function() {
         var parts          = [],
             dependencyIds  = objects.values(options.dependencies),
-            dependencyVars = objects.keys(options.dependencies),
+            dependencyVars = Object.keys(options.dependencies),
             dependencies   = '['
               + dependencyIds.map(
                   function(id) { return '"' + js.stringEscape(id) + '"'; }
diff --git a/lib/utils/objects.js b/lib/utils/objects.js
index 09587c1..6973095 100644
--- a/lib/utils/objects.js
+++ b/lib/utils/objects.js
@@ -2,18 +2,6 @@
 
 /* Object utilities. */
 var objects = {
-  keys: function(object) {
-    var result = [], key;
-
-    for (key in object) {
-      if (object.hasOwnProperty(key)) {
-        result.push(key);
-      }
-    }
-
-    return result;
-  },
-
   values: function(object) {
     var result = [], key;