diff --git a/matrix_pygmalion_bot/core.py b/matrix_pygmalion_bot/core.py
index 253f897..01796c9 100644
--- a/matrix_pygmalion_bot/core.py
+++ b/matrix_pygmalion_bot/core.py
@@ -147,7 +147,7 @@ class Callbacks(object):
 
         elif event.body.startswith('!image_negative_prompt'):
             negative_prompt = event.body.removeprefix('!image_negative_prompt').strip()
-            if len(prompt) > 0:
+            if len(negative_prompt) > 0:
                 self.bot.negative_prompt = negative_prompt
             else:
                 self.bot.negative_prompt = None
@@ -193,6 +193,9 @@ class Callbacks(object):
             new_answer = event.body.removeprefix('!replace').strip()
             await self.bot.send_message(self.client, room.room_id, new_answer, reply_to=chat_history_item.relates_to_event)
             return
+        elif event.body.startswith('!'):
+            await self.bot.send_message(self.client, room.room_id, "UNKNOWN COMMAND")
+            return
 
         # Other commands
         if re.search("^(?=.*\bsend\b)(?=.*\bpicture\b).*$", event.body):