diff --git a/underscore.js b/underscore.js
index 60bf47ccd..66f83dbfb 100644
--- a/underscore.js
+++ b/underscore.js
@@ -525,7 +525,7 @@
 
   // Is a given variable an arguments object?
   _.isArguments = function(obj) {
-    return obj && obj.callee;
+    return !!(obj && obj.callee);
   };
 
   // Is a given value a function?