diff --git a/lodash.js b/lodash.js
index 6cd4623aa..067a55cef 100644
--- a/lodash.js
+++ b/lodash.js
@@ -5559,7 +5559,7 @@
       thisArg = newData[2];
       partials = newData[3];
       holders = newData[4];
-      arity = newData[9] = newData[9] == null
+      arity = newData[9] = newData[9] === undefined
         ? (isBindKey ? 0 : func.length)
         : nativeMax(newData[9] - length, 0);