diff --git a/Source/JavaScriptCore/runtime/ErrorInstance.cpp b/Source/JavaScriptCore/runtime/ErrorInstance.cpp
index e8d226ea9dc1f..e77be60ea99cf 100644
--- a/Source/JavaScriptCore/runtime/ErrorInstance.cpp
+++ b/Source/JavaScriptCore/runtime/ErrorInstance.cpp
@@ -281,7 +281,7 @@ String ErrorInstance::sanitizedNameString(JSGlobalObject* globalObject)
     }
     RETURN_IF_EXCEPTION(scope, {});
 
-    if (!nameValue || !nameValue.isPrimitive())
+    if (!nameValue || !nameValue.isPrimitive() || nameValue.isUndefined())
         return "Error"_s;
     RELEASE_AND_RETURN(scope, nameValue.toWTFString(globalObject));
 }