--- a/eric7/WebBrowser/AdBlock/AdBlockManager.py	Sun Aug 29 20:21:41 2021 +0200
+++ b/eric7/WebBrowser/AdBlock/AdBlockManager.py	Mon Aug 30 20:02:39 2021 +0200
@@ -425,7 +425,7 @@
         else:
             subscriptions = (
                 [self.__defaultSubscriptionUrlString] +
-                self.__additionalDefaultSubscriptionUrlStrings +
+                list(self.__additionalDefaultSubscriptionUrlStrings) +
                 [self.__customSubscriptionUrlString]
             )
         for subscription in subscriptions: