diff --git a/discord/http.py b/discord/http.py
index 6e726f87c..d1556e303 100644
--- a/discord/http.py
+++ b/discord/http.py
@@ -497,7 +497,7 @@ class HTTPClient:
     def ban(self, user_id, guild_id, delete_message_days=1, reason=None):
         r = Route('PUT', '/guilds/{guild_id}/bans/{user_id}', guild_id=guild_id, user_id=user_id)
         params = {
-            'delete-message-days': delete_message_days,
+            'delete_message_days': delete_message_days,
         }
 
         if reason: