diff --git a/Foundation/CPDictionary.j b/Foundation/CPDictionary.j
index 593558502..1c6238a2b 100755
--- a/Foundation/CPDictionary.j
+++ b/Foundation/CPDictionary.j
@@ -236,7 +236,7 @@
         if (lhsObject === rhsObject)
             continue;
             
-        if ([lhsObject respondsToSelector:@selector(isEqual:)] && [lhsObject isEqual:rhsObject])
+        if (lhsObject.isa && rhsObject.isa && [lhsObject respondsToSelector:@selector(isEqual:)] && [lhsObject isEqual:rhsObject])
             continue;
         
         return NO;