Maybe it's subject for separate issue — but it is good finding. http://codereview.appspot.com/6425052/diff/1/Objects/classobject.c File Objects/classobject.c (right): http://codereview.appspot.com/6425052/diff/1/Objects/classobject.c#newcode248 Objects/classobject.c:248: Py_XDECREF(funcname); Looks like you found refleak. It should be fixed anyway