diff --git a/lodash.js b/lodash.js
index 1ff5b6844..19579ee95 100644
--- a/lodash.js
+++ b/lodash.js
@@ -121,10 +121,10 @@
       isV8 = nativeBind && !/\n|true/.test(nativeBind + isIeOpera);
 
   /* Detect if `Function#bind` exists and is inferred to be fast (all but V8) */
-  var isBindFast = !isV8;
+  var isBindFast = nativeBind && !isV8;
 
   /* Detect if `Object.keys` exists and is inferred to be fast (IE, Opera, V8) */
-  var isKeysFast = isIeOpera || isV8;
+  var isKeysFast = nativeKeys && (isIeOpera || isV8);
 
   /**
    * Detect the JScript [[DontEnum]] bug: