diff --git a/plugins/Observer.py b/plugins/Observer.py
index 76996d461..bc8831409 100644
--- a/plugins/Observer.py
+++ b/plugins/Observer.py
@@ -136,7 +136,7 @@ class Observer(callbacks.Privmsg):
             m = r.search(msg.args[1])
             if m is not None:
                 command = observer.command()
-                groups = list(m.groups())
+                groups = filter(None, list(m.groups()))
                 groups.insert(0, m.group(0))
                 for (i, group) in enumerate(groups):
                     command = command.replace('$%s' % i, group)
diff --git a/test/test_Observer.py b/test/test_Observer.py
index 2ca873073..33723ca4b 100644
--- a/test/test_Observer.py
+++ b/test/test_Observer.py
@@ -75,5 +75,10 @@ class ObserverTestCase(ChannelPluginTestCase):
         self.assertNotError('remove foo')
         self.assertRegexp('observer list', 'no relevant')
 
+    def testObserverWithEmptyGroup(self):
+        self.assertNotError('add foo m/foo(bar)?/i echo I saw foo.')
+        self.assertNotError('observer enable foo')
+        self.assertSnarfRegexp('foo', 'saw foo')
+
 # vim:set shiftwidth=4 tabstop=8 expandtab textwidth=78: