jackalope/jackalope — comment on commit bd07f4d60dd2a1d4632da6dbd925bd41c67ff4b0
File: src/Jackalope/ObjectManager.php line 1601
By dbu:

i think you should use $node->isNodeType to check for mix:lockable (it could be of a type inheriting from mix:lockable for instance, or it could have more than 1 mixin type)