diff --git a/src/callbacks.py b/src/callbacks.py
index 64fac300a..d2d6ba4b9 100644
--- a/src/callbacks.py
+++ b/src/callbacks.py
@@ -1036,11 +1036,20 @@ class BasePlugin(object):
                 cb.log = log.getPluginLogger('%s.%s' % (self.name(),cb.name()))
         super(BasePlugin, self).__init__(*args, **kwargs)
 
+class SynchronizedAndFirewalled(log.MetaFirewall, utils.python.Synchronized):
+    pass # Necessary for the metaclass compatibility issue.
+
 class Commands(BasePlugin):
     # For awhile, a comment stood here to say, "Eventually callCommand."  But
     # that's wrong, because we can't do generic error handling in this
     # callCommand -- plugins need to be able to override callCommand and do
     # error handling there (see the Http plugin for an example).
+    __metaclass__ = SynchronizedAndFirewalled
+    __synchronized__ = (
+        '__call__',
+        'callCommand',
+        'invalidCommand',
+        )
     __firewalled__ = {'isCommand': None,
                       '_callCommand': None}
     commandArgs = ['self', 'irc', 'msg', 'args']
@@ -1049,6 +1058,9 @@ class Commands(BasePlugin):
     def name(self):
         return self.__class__.__name__
 
+    def __call__(self, *args, **kwargs):
+        super(Commands, self).__call__(*args, **kwargs)
+
     def canonicalName(self):
         return canonicalName(self.name())