diff --git a/Modules/_abc.c b/Modules/_abc.c
index aa091c7..562a2e6 100644
--- a/Modules/_abc.c
+++ b/Modules/_abc.c
@@ -647,9 +647,7 @@
     assert(PyTuple_Check(mro));
     for (pos = 0; pos < PyTuple_GET_SIZE(mro); pos++) {
         PyObject *mro_item = PyTuple_GET_ITEM(mro, pos);
-        if (mro_item == NULL) {
-            goto end;
-        }
+        assert(mro_item != NULL);
         if ((PyObject *)self == mro_item) {
             if (_add_to_weak_set(&impl->_abc_cache, subclass) < 0) {
                 goto end;