diff --git a/libraries/botframework-connector/botframework/connector/auth/skill_validation.py b/libraries/botframework-connector/botframework/connector/auth/skill_validation.py
index b708e27cb..8c35f1b0a 100644
--- a/libraries/botframework-connector/botframework/connector/auth/skill_validation.py
+++ b/libraries/botframework-connector/botframework/connector/auth/skill_validation.py
@@ -120,7 +120,7 @@ async def authenticate_channel_token(
         )
 
         if auth_configuration.valid_token_issuers:
-            token_validation_parameters.issuer.append(
+            token_validation_parameters.issuer.extend(
                 auth_configuration.valid_token_issuers
             )