diff --git a/scripts/supybot-wizard b/scripts/supybot-wizard
index dc39530c4..56972ce20 100755
--- a/scripts/supybot-wizard
+++ b/scripts/supybot-wizard
@@ -383,7 +383,8 @@ def main():
                 # FIXME: say which ones weren't channels.
                 output("""Not all of those are valid IRC channels.  Be sure to
                 prefix the channel with # (or +, or !, or &, but no one uses
-                those channels, really).""")
+                those channels, really).  Be sure the channel key (if you are
+                supplying one) does not contain a comma.""")
     else:
         conf.supybot.channels.setValue([])
 
diff --git a/src/conf.py b/src/conf.py
index 06a3c1881..1bad0f677 100644
--- a/src/conf.py
+++ b/src/conf.py
@@ -168,7 +168,13 @@ class ValidChannel(registry.String):
     """Value must be a valid IRC channel name."""
     def setValue(self, v):
         if ',' in v:
-            (channel, _) = v.split(',', 1)
+            # To prevent stupid users from: a) trying to add a channel key
+            # with a comma in it, b) trying to add channels separated by
+            # commas instead of spaces
+            try:
+                (channel, _) = v.split(',')
+            except ValueError:
+                self.error()
         else:
             channel = v
         if not ircutils.isChannel(channel):