diff --git a/matrix_reminder_bot/reminder.py b/matrix_reminder_bot/reminder.py
index e362f44..b77b3c0 100644
--- a/matrix_reminder_bot/reminder.py
+++ b/matrix_reminder_bot/reminder.py
@@ -160,8 +160,8 @@ async def _fire_alarm(self):
             self.room_id,
             message,
             notice=False,
-            mentions_user_ids=[self.target_user] if self.has_target() else [],
-            mentions_room=self.has_target(),
+            mentions_user_ids=[self.target_user] if self.has_target() else None,
+            mentions_room=not self.has_target(),
         )
 
     def cancel(self, cancel_alarm: bool = True):