diff --git a/src/util.h b/src/util.h
index f0fc6097313fe8..0a770110ab579e 100644
--- a/src/util.h
+++ b/src/util.h
@@ -760,6 +760,7 @@ class PersistentToLocal {
   template <class TypeName>
   static inline v8::Local<TypeName> Strong(
       const v8::PersistentBase<TypeName>& persistent) {
+    DCHECK(!persistent.IsWeak());
     return *reinterpret_cast<v8::Local<TypeName>*>(
         const_cast<v8::PersistentBase<TypeName>*>(&persistent));
   }