diff --git a/deps/v8/src/objects/js-objects.cc b/deps/v8/src/objects/js-objects.cc
index e5a03dff14835e..91433bc8e0ca74 100644
--- a/deps/v8/src/objects/js-objects.cc
+++ b/deps/v8/src/objects/js-objects.cc
@@ -432,7 +432,7 @@ Maybe<bool> JSReceiver::SetOrCopyDataProperties(
       Nothing<bool>());
 
   if (!from->HasFastProperties() && target->HasFastProperties() &&
-      !IsJSGlobalProxy(*target)) {
+      IsJSObject(*target) && !IsJSGlobalProxy(*target)) {
     // JSProxy is always in slow-mode.
     DCHECK(!IsJSProxy(*target));
     // Convert to slow properties if we're guaranteed to overflow the number of