diff --git a/lib/nodes.js b/lib/nodes.js
index 026e7cfd..2fb2d273 100644
--- a/lib/nodes.js
+++ b/lib/nodes.js
@@ -1480,7 +1480,14 @@
       return "(" + (tests.join(' || ')) + ")";
     };
     In.prototype.compileLoopTest = function(o) {
-      return "" + (utility('inArray')) + "(" + (this.object.compile(o)) + ", " + (this.array.compile(o)) + ")";
+      var _ref2, obj1, obj2, prefix;
+      _ref2 = this.object.compileReference(merge(o, {
+        top: true
+      }), {
+        precompile: true
+      }), obj1 = _ref2[0], obj2 = _ref2[1];
+      prefix = obj1 !== obj2 ? ("" + obj1 + ", ") : '';
+      return "(" + prefix + (utility('indexOf')) + ".call(" + (this.array.compile(o)) + ", " + obj2 + ") >= 0)";
     };
     return In;
   })();
@@ -1946,7 +1953,7 @@
   UTILITIES = {
     "extends": 'function(child, parent) {\n  function ctor() { this.constructor = child; }\n  ctor.prototype = parent.prototype;\n  child.prototype = new ctor;\n  if (typeof parent.extended === "function") parent.extended(child);\n  child.__super__ = parent.prototype;\n}',
     bind: 'function(func, context) {\n  return function() { return func.apply(context, arguments); };\n}',
-    inArray: '(function() {\n  var indexOf = Array.prototype.indexOf || function(item) {\n    var i = this.length; while (i--) if (this[i] === item) return i;\n    return -1;\n  };\n  return function(item, array) { return indexOf.call(array, item) > -1; };\n})()',
+    indexOf: 'Array.prototype.indexOf || function(item) {\n  for (var i = 0, l = this.length; i < l; i++) if (this[i] === item) return i;\n  return -1;\n}',
     hasProp: 'Object.prototype.hasOwnProperty',
     slice: 'Array.prototype.slice'
   };
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 2349727d..0730717c 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -1262,7 +1262,9 @@ exports.In = class In extends Base
     "(#{tests.join(' || ')})"
 
   compileLoopTest: (o) ->
-    "#{utility 'inArray'}(#{@object.compile o}, #{@array.compile o})"
+    [obj1, obj2] = @object.compileReference merge(o, top: yes), precompile: yes
+    prefix = if obj1 isnt obj2 then "#{obj1}, " else ''
+    "(#{prefix}#{utility 'indexOf'}.call(#{@array.compile o}, #{obj2}) >= 0)"
 
 #### Try
 
@@ -1462,7 +1464,7 @@ exports.For = class For extends Base
         unstepPart = "\n#{@tab}" + unstepPart
     if @object
       forPart     = "#{ivar} in #{sourcePart}"
-      guardPart   = "\n#{idt1}if (!#{utility('hasProp')}.call(#{svar}, #{ivar})) continue;" unless @raw  
+      guardPart   = "\n#{idt1}if (!#{utility('hasProp')}.call(#{svar}, #{ivar})) continue;" unless @raw
     body          = body.compile merge o, indent: idt1, top: true
     vars          = if range then name else "#{name}, #{ivar}"
     """
@@ -1663,16 +1665,13 @@ UTILITIES =
       return function() { return func.apply(context, arguments); };
     }
   '''
-  
+
   # Discover if an item is in an array.
-  inArray: '''
-    (function() {
-      var indexOf = Array.prototype.indexOf || function(item) {
-        var i = this.length; while (i--) if (this[i] === item) return i;
-        return -1;
-      };
-      return function(item, array) { return indexOf.call(array, item) > -1; };
-    })()
+  indexOf: '''
+    Array.prototype.indexOf || function(item) {
+      for (var i = 0, l = this.length; i < l; i++) if (this[i] === item) return i;
+      return -1;
+    }
   '''
 
   # Shortcuts to speed up the lookup time for native functions.