diff --git a/py/proto.c b/py/proto.c
index 9f110b9f9a..14fbaeee8d 100644
--- a/py/proto.c
+++ b/py/proto.c
@@ -31,7 +31,7 @@
 #ifndef MICROPY_UNSAFE_PROTO
 const void *mp_proto_get(uint16_t name, mp_const_obj_t obj) {
     const mp_obj_type_t *type = mp_obj_get_type(obj);
-    const void *protocol = mp_type_get_protocol_slot(type);
+    const void *protocol = MP_OBJ_TYPE_GET_SLOT_OR_NULL(type, protocol);
     if (!protocol) {
         return NULL;
     }
diff --git a/py/proto.h b/py/proto.h
index a7b9b523f2..19e75a67fc 100644
--- a/py/proto.h
+++ b/py/proto.h
@@ -31,7 +31,7 @@
 #define MP_PROTOCOL_HEAD /* NOTHING */
 #define MP_PROTO_IMPLEMENT(name) /* NOTHING */
 static inline void *mp_proto_get(uint16_t name, mp_const_obj_type_t obj) {
-    return mp_type_get_protocol_slot(mp_obj_get_type(obj));
+    return MP_OBJ_TYPE_GET_SLOT_OR_NULL(mp_obj_get_type(obj), protocol);
 }
 #else
 #define MP_PROTOCOL_HEAD \