diff -r 82d95ae3d2c8 pypy/module/cpyext/typeobject.py
--- a/pypy/module/cpyext/typeobject.py	Tue Jul 25 20:19:44 2017 +0200
+++ b/pypy/module/cpyext/typeobject.py	Wed Jul 26 19:17:05 2017 +0300
@@ -757,11 +757,8 @@
         # only for the exact type, like 'space.w_tuple' or 'space.w_list'
         pto.c_tp_dealloc = typedescr.get_dealloc().get_llhelper(space)
     else:
-        # for all subtypes, use base's dealloc (requires sorting in attach_all)
-        pto.c_tp_dealloc = pto.c_tp_base.c_tp_dealloc
-        if not pto.c_tp_dealloc:
-            # strange, but happens (ABCMeta)
-            pto.c_tp_dealloc = llslot(space, subtype_dealloc)
+        # always assign to subtype_dealloc
+        pto.c_tp_dealloc = subtype_dealloc.api_func.get_llhelper(space)
 
     if builder.cpyext_type_init is not None:
         builder.cpyext_type_init.append((pto, w_type))