diff --git a/redbot/core/core_commands.py b/redbot/core/core_commands.py
index 5e6050f69..ec8c82a5b 100644
--- a/redbot/core/core_commands.py
+++ b/redbot/core/core_commands.py
@@ -1257,7 +1257,7 @@ class Core(CoreLogic):
 
         msg = _("Whitelisted Users:")
         for user in curr_list:
-            msg.append("\n\t- {}".format(user))
+            msg += "\n\t- {}".format(user)
 
         for page in pagify(msg):
             await ctx.send(box(page))
@@ -1320,7 +1320,7 @@ class Core(CoreLogic):
 
         msg = _("blacklisted Users:")
         for user in curr_list:
-            msg.append("\n\t- {}".format(user))
+            msg += "\n\t- {}".format(user)
 
         for page in pagify(msg):
             await ctx.send(box(page))