diff --git a/redbot/cogs/cleanup/cleanup.py b/redbot/cogs/cleanup/cleanup.py
index 67bb8b3d6..04ff18bcf 100644
--- a/redbot/cogs/cleanup/cleanup.py
+++ b/redbot/cogs/cleanup/cleanup.py
@@ -221,14 +221,9 @@ class Cleanup:
         author = ctx.message.author
         is_bot = self.bot.user.bot
 
-        prefixes = self.bot.command_prefix
+        prefixes = await self.bot.get_prefix(ctx.message) # This returns all server prefixes
         if isinstance(prefixes, str):
             prefixes = [prefixes]
-        elif callable(prefixes):
-            if asyncio.iscoroutine(prefixes):
-                await ctx.send(_('Coroutine prefixes not yet implemented.'))
-                return
-            prefixes = prefixes(self.bot, ctx.message)
 
         # In case some idiot sets a null prefix
         if '' in prefixes:
@@ -241,7 +236,8 @@ class Cleanup:
                 return True
             p = discord.utils.find(m.content.startswith, prefixes)
             if p and len(p) > 0:
-                return m.content[len(p):].startswith(tuple(self.bot.commands))
+                cmd_name = m.content[len(p):].split(' ')[0]
+                return bool(self.bot.get_command(cmd_name))
             return False
 
         to_delete = [ctx.message]