diff --git a/lambdabot-irc-plugins.cabal b/lambdabot-irc-plugins.cabal
--- a/lambdabot-irc-plugins.cabal
+++ b/lambdabot-irc-plugins.cabal
@@ -1,5 +1,5 @@
 name:                   lambdabot-irc-plugins
-version:                5.1
+version:                5.1.0.1
 
 license:                GPL
 license-file:           LICENSE
@@ -22,7 +22,7 @@
                         .
                         [topic] Modify channel topics.
 
-homepage:               http://haskell.org/haskellwiki/Lambdabot
+homepage:               https://wiki.haskell.org/Lambdabot
 
 build-type:             Simple
 cabal-version:          >= 1.8
diff --git a/src/Lambdabot/Plugin/IRC/IRC.hs b/src/Lambdabot/Plugin/IRC/IRC.hs
--- a/src/Lambdabot/Plugin/IRC/IRC.hs
+++ b/src/Lambdabot/Plugin/IRC/IRC.hs
@@ -81,12 +81,18 @@
           . encodeParams (ircMsgParams msg)
   where
     encodePrefix [] = id
-    encodePrefix prefix = showChar ':' . showString prefix . showChar ' '
+    encodePrefix prefix = showChar ':' . showString' prefix . showChar ' '
 
     encodeCommand cmd = showString cmd
 
     encodeParams [] = id
-    encodeParams (p:ps) = showChar ' ' . showString p . encodeParams ps
+    encodeParams (p:ps) = showChar ' ' . showString' p . encodeParams ps
+
+    -- IrcMessage is supposed to contain strings that are lists of bytes, but
+    -- if a plugin messes up the encoding then we may end up with arbitrary
+    -- Unicode codepoints. This is dangerous (\x10a would produce a newline!),
+    -- so we sanitize the message here.
+    showString' = showString . map (\c -> if c > '\xFF' then '?' else c)
 
 -- | 'decodeMessage' Takes an input line from the IRC protocol stream
 --   and decodes it into a message.  TODO: this has too many parameters.