diff --git a/plugins/String/plugin.py b/plugins/String/plugin.py
index bfebd73f0..b68e96497 100644
--- a/plugins/String/plugin.py
+++ b/plugins/String/plugin.py
@@ -1,6 +1,6 @@
 ###
 # Copyright (c) 2003-2005, Jeremiah Fincher
-# Copyright (c) 2008, James Vega
+# Copyright (c) 2008-2009, James Vega
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -29,6 +29,7 @@
 ###
 
 import types
+import binascii
 
 import supybot.utils as utils
 from supybot.commands import *
@@ -81,6 +82,10 @@ class String(callbacks.Plugin):
             irc.reply(text.decode(encoding).encode('utf-8'))
         except LookupError:
             irc.errorInvalid('encoding', encoding)
+        except binascii.Error:
+            irc.errorInvalid('base64 string',
+                             s='Base64 strings must be a multiple of 4 in '
+                               'length, padded with \'=\' if necessary.')
     decode = wrap(decode, ['something', 'text'])
 
     def levenshtein(self, irc, msg, args, s1, s2):
diff --git a/plugins/String/test.py b/plugins/String/test.py
index a50e4552a..f86d9e38b 100644
--- a/plugins/String/test.py
+++ b/plugins/String/test.py
@@ -1,5 +1,6 @@
 ###
 # Copyright (c) 2003-2005, Jeremiah Fincher
+# Copyright (c) 2009, James Vega
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -104,6 +105,7 @@ class StringTestCase(PluginTestCase):
         self.assertNotRegexp('encode aldkfja foobar', 'LookupError')
         self.assertNotRegexp('decode asdflkj foobar', 'LookupError')
         self.assertResponse('decode zlib [encode zlib %s]' % s, s)
+        self.assertRegexp('decode base64 $BCfBg7;9D;R(B', 'padded with')
 
     def testRe(self):
         self.assertResponse('re "m/system time/" [status cpu]', 'system time')