index d545c34..91cb151 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -738,7 +738,7 @@ BUILTIN(ArrayConcat) {
   int result_len = 0;
   for (int i = 0; i < n_arguments; i++) {
     Object* arg = args[i];
-    if (!arg->IsJSArray() || JSArray::cast(arg)->HasFastElements()) {
+    if (!arg->IsJSArray() || !JSArray::cast(arg)->HasFastElements()) {
       return CallJsBuiltin("ArrayConcat", args);
     }
This reverts 4153.
    # Please enter the commit message for your changes. Lines starting

Review URL: http://codereview.chromium.org/1055003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4154 ce2b1a6d-e550-0410-aec6-3dcde31c8c00