diff --git a/test/index.html b/test/index.html
index a62477ab5..40b06b4fb 100644
--- a/test/index.html
+++ b/test/index.html
@@ -42,7 +42,7 @@
 				Object.keys = function() {};
 
 				String.prototype._contains = String.prototype.contains;
-				String.prototype.contains = function() {};
+				String.prototype.contains = String.prototype._contains ? function() {} : Boolean;
 
 				window.WinRTError = Error;
 
diff --git a/test/test.js b/test/test.js
index 9d6dd229f..c8742a9c6 100644
--- a/test/test.js
+++ b/test/test.js
@@ -262,7 +262,7 @@
         Object.keys = function() {};
 
         var _contains = String.prototype.contains;
-        String.prototype.contains = function() {};
+        String.prototype.contains = _contains ? function() {} : Boolean;
 
         // load Lo-Dash and expose it to the bad extensions/shims
         lodashBizarro = (lodashBizarro = require(filePath))._ || lodashBizarro;
@@ -275,8 +275,8 @@
         Object.getPrototypeOf = _getPrototypeOf;
         Object.keys = _keys;
 
-        if (String.prototype._contains) {
-          String.prototype.contains = String.prototype._contains;
+        if (_contains) {
+          String.prototype.contains = _contains;
         } else {
           delete String.prototype.contains;
         }