diff --git a/twilio/authStrategy/__init__.py b/twilio/authStrategy/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/twilio/authStrategy/authStrategy.py b/twilio/authStrategy/authStrategy.py
index 55b901848..901a6b4b7 100644
--- a/twilio/authStrategy/authStrategy.py
+++ b/twilio/authStrategy/authStrategy.py
@@ -11,6 +11,7 @@ def __init__(self, auth_type: AuthType):
     def auth_type(self) -> AuthType:
         return self._auth_type
 
+    @abstractmethod
     def get_auth_string(self) -> str:
         """Return the authentication string."""
         pass