en_sit will be freed when en is DECREF'd.  Don't double free.
diff --git a/Objects/enumobject.c b/Objects/enumobject.c
index a9d4a5e..8c3eab1 100644
--- a/Objects/enumobject.c
+++ b/Objects/enumobject.c
@@ -33,7 +33,6 @@
 	}
 	en->en_result = PyTuple_Pack(2, Py_None, Py_None);
 	if (en->en_result == NULL) {
-		Py_DECREF(en->en_sit);
 		Py_DECREF(en);
 		return NULL;
 	}