diff --git a/deepmd/op/__init__.py b/deepmd/op/__init__.py
index 1771422a40..3700bf175e 100644
--- a/deepmd/op/__init__.py
+++ b/deepmd/op/__init__.py
@@ -4,7 +4,7 @@
 import importlib
 import logging
 
-NOT_LOADABLE = ("__init__.py")
+NOT_LOADABLE = ("__init__.py",)
 PACKAGE_BASE = "deepmd.op"
 
 log = logging.getLogger(__name__)