diff --git a/ProtoText/hook_helper.py b/ProtoText/hook_helper.py
index 7ef4cd1..64dd5a9 100644
--- a/ProtoText/hook_helper.py
+++ b/ProtoText/hook_helper.py
@@ -1,5 +1,5 @@
 import types
-import __builtin__
+import builtins
 import logging
 
 HOOK_TABLE_NAME = '__ZX_PY_HOOK_TABLE__'
@@ -14,11 +14,11 @@ def register_class_hook(cls, strategy='safe', skip_buildin=True):
     :param skip_buildin: determine if we skip the build in object
     :return:
     """
-    assert isinstance(cls, (type, types.ClassType)), \
+    assert isinstance(cls, type), \
         "The input object must be a class object"
     base_classes = cls.__bases__
     for base_class in base_classes:
-        if skip_buildin and base_class.__name__ in __builtin__.__dict__:
+        if skip_buildin and base_class.__name__ in builtins.__dict__:
             logger.warn("Skip hooking build-in base class '%s' in sub-class '%s' ..." %
                         (base_class.__name__, cls.__name__))
             continue
@@ -49,7 +49,7 @@ def deregister_class_hook(cls):
     :param cls:  the class object of the class to unhook
     :return:
     """
-    assert isinstance(cls, (type, types.ClassType)), \
+    assert isinstance(cls, type), \
         "The input object must be a class object"
     base_classes = cls.__bases__
     for base_class in base_classes:
@@ -63,4 +63,4 @@ def deregister_class_hook(cls):
                 setattr(base_class, x, _hook_table[x])
             else:
                 delattr(base_class, x)
-        delattr(base_class, HOOK_TABLE_NAME)
\ No newline at end of file
+        delattr(base_class, HOOK_TABLE_NAME)