diff --git a/plugins/Filter/plugin.py b/plugins/Filter/plugin.py
index fcc247116..e995aa125 100644
--- a/plugins/Filter/plugin.py
+++ b/plugins/Filter/plugin.py
@@ -158,12 +158,15 @@ class Filter(callbacks.Plugin):
 
     def unbinary(self, irc, msg, args, text):
         """<text>
-        
+
         Returns the character representation of binary <text>.
         Assumes ASCII, 8 digits per character.
         """
-        L = [chr(int(text[i:(i+8)], 2)) for i in xrange(0, len(text), 8)]
-        irc.reply(''.join(L))
+        try:
+            L = [chr(int(text[i:(i+8)], 2)) for i in xrange(0, len(text), 8)]
+            irc.reply(''.join(L))
+        except ValueError:
+            irc.errorInvalid('binary string', text)
     unbinary = wrap(unbinary, ['text'])
 
     def hexlify(self, irc, msg, args, text):
diff --git a/plugins/Filter/test.py b/plugins/Filter/test.py
index 2a73e5f9f..0a66da62b 100644
--- a/plugins/Filter/test.py
+++ b/plugins/Filter/test.py
@@ -89,6 +89,7 @@ class FilterTest(ChannelPluginTestCase):
 
     def testUnbinary(self):
         self.assertResponse('unbinary 011011010110111101101111', 'moo')
+        self.assertError('unbinary moo')
 
     def testRot13(self):
         for s in map(str, range(1000, 1010)):