1 files changed, 2 insertions, 0 deletions
diff --git a/Lib/typing.py b/Lib/typing.py
index fe22b2b..c7fe5dd 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1503,6 +1503,8 @@ class _ProtocolMeta(GenericMeta):
     """
 
     def __instancecheck__(self, obj):
+        if _Protocol not in self.__bases__:
+            return super().__instancecheck__(obj)
         raise TypeError("Protocols cannot be used with isinstance().")
 
     def __subclasscheck__(self, cls):