Hi, changeset https://hg.python.org/cpython/rev/e7062dd9085e in the 2.7 branch changes how tp_new is assigned, and causes regressions with multiple inheritance from extension classes. http://bugs.python.org/issue25731#msg262922 has a fairly simple reproducer using cython. The __base__ attribute is set correctly, but tp_new is now wrong and thus the object initialization is broken. Can this change be fixed or reverted before the next 2.7.x release? (I have not verified if this regression also affects the 3.5 branch) Thanks, Julien