diff --git a/src/google/protobuf/dynamic_message.cc b/src/google/protobuf/dynamic_message.cc
index caf592eee04b4..631aa798d83ac 100644
--- a/src/google/protobuf/dynamic_message.cc
+++ b/src/google/protobuf/dynamic_message.cc
@@ -383,7 +383,11 @@ struct DynamicMessageFactory::TypeInfo {
           &DynamicMessage::MergeImpl,
           internal::MessageCreator(),  // to be filled later
           &DynamicMessage::DestroyImpl,
+#if defined(PROTOBUF_CUSTOM_VTABLE)
           static_cast<void (MessageLite::*)()>(&DynamicMessage::ClearImpl),
+#else
+          nullptr,
+#endif  // PROTOBUF_CUSTOM_VTABLE
           DynamicMessage::ByteSizeLongImpl,
           DynamicMessage::_InternalSerializeImpl,
           PROTOBUF_FIELD_OFFSET(DynamicMessage, cached_byte_size_),
diff --git a/src/google/protobuf/implicit_weak_message.cc b/src/google/protobuf/implicit_weak_message.cc
index d53daf64780e6..73b2fa7639f57 100644
--- a/src/google/protobuf/implicit_weak_message.cc
+++ b/src/google/protobuf/implicit_weak_message.cc
@@ -73,7 +73,11 @@ constexpr ClassDataLite<1> ImplicitWeakMessage::class_data_ = {
                                  sizeof(ImplicitWeakMessage),
                                  alignof(ImplicitWeakMessage)),
         &DestroyImpl,
+#if defined(PROTOBUF_CUSTOM_VTABLE)
         GetClearImpl<ImplicitWeakMessage>(),
+#else
+       nullptr,
+#endif  // PROTOBUF_CUSTOM_VTABLE
         &ByteSizeLongImpl,
         &_InternalSerializeImpl,
         PROTOBUF_FIELD_OFFSET(ImplicitWeakMessage, cached_size_),