diff --git a/rerunbot.py b/rerunbot.py
index c41253e..ea379cb 100644
--- a/rerunbot.py
+++ b/rerunbot.py
@@ -116,7 +116,8 @@ class ReplayBot(irc.bot.SingleServerIRCBot):
         if int(tags['user-id']) != self.control_user:
             send_response('Sorry @{0}, you are not allowed to do this'.format(tags['display-name']))
             return
-        self.reactor.scheduler.queue.clear()
+        with self.reactor.mutex:
+            self.reactor.scheduler.queue.clear()
 
     def _post_message(self, user, msg):
         self.connection.privmsg(self.output_channel, '[{0}]: {1}'.format(user, msg))