diff --git a/Modules/collectionsmodule.c b/Modules/collectionsmodule.c
index e49224d..368f0b6 100644
--- a/Modules/collectionsmodule.c
+++ b/Modules/collectionsmodule.c
@@ -587,7 +587,8 @@
 	PyObject *it1=NULL, *it2=NULL, *x, *y;
 	int i, b, vs, ws, minlen, cmp=-1;
 
-	if (v->ob_type != &deque_type || w->ob_type != &deque_type) {
+	if (!PyObject_TypeCheck(v, &deque_type) || 
+	    !PyObject_TypeCheck(w, &deque_type)) {
 		Py_INCREF(Py_NotImplemented);
 		return Py_NotImplemented;
 	}