Use PyDict_Contains() instead of PySequence_Contains().
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index ec4ea56..7d523cf 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -690,7 +690,7 @@
 static int
 proxy_contains(proxyobject *pp, PyObject *key)
 {
-	return PySequence_Contains(pp->dict, key);
+	return PyDict_Contains(pp->dict, key);
 }
 
 static PySequenceMethods proxy_as_sequence = {
@@ -709,7 +709,7 @@
 static PyObject *
 proxy_has_key(proxyobject *pp, PyObject *key)
 {
-	int res = PySequence_Contains(pp->dict, key);
+	int res = PyDict_Contains(pp->dict, key);
 	if (res < 0)
 		return NULL;
 	return PyBool_FromLong(res);