diff --git a/yesod-core/Yesod/Internal/Core.hs b/yesod-core/Yesod/Internal/Core.hs
index 0ca66793..6693bb88 100644
--- a/yesod-core/Yesod/Internal/Core.hs
+++ b/yesod-core/Yesod/Internal/Core.hs
@@ -356,15 +356,16 @@ defaultYesodRunner s master toMasterRoute mkey murl handler req = do
                    $ filter (\(x, _) -> x /= nonceKey) session'
     yar <- handlerToYAR master s toMasterRoute (yesodRender master) errorHandler rr murl sessionMap h
     let mnonce = reqNonce rr
-    return $ yarToResponse (hr mnonce getExpires host exp') yar
+    iv <- liftIO CS.randomIV
+    return $ yarToResponse (hr iv mnonce getExpires host exp') yar
   where
-    hr mnonce getExpires host exp' hs ct sm =
+    hr iv mnonce getExpires host exp' hs ct sm =
         hs'''
       where
         sessionVal =
             case (mkey, mnonce) of
                 (Just key, Just nonce)
-                    -> encodeSession key exp' host
+                    -> encodeSession key iv exp' host
                      $ Map.toList
                      $ Map.insert nonceKey nonce sm
                 _ -> mempty
diff --git a/yesod-core/Yesod/Internal/Session.hs b/yesod-core/Yesod/Internal/Session.hs
index 7e840136..15122adf 100644
--- a/yesod-core/Yesod/Internal/Session.hs
+++ b/yesod-core/Yesod/Internal/Session.hs
@@ -12,12 +12,13 @@ import Data.Text (Text, pack, unpack)
 import Control.Arrow ((***))
 
 encodeSession :: CS.Key
+              -> CS.IV
               -> UTCTime -- ^ expire time
               -> ByteString -- ^ remote host
               -> [(Text, Text)] -- ^ session
               -> ByteString -- ^ cookie value
-encodeSession key expire rhost session' =
-    CS.encrypt key $ encode $ SessionCookie expire rhost session'
+encodeSession key iv expire rhost session' =
+    CS.encrypt key iv $ encode $ SessionCookie expire rhost session'
 
 decodeSession :: CS.Key
               -> UTCTime -- ^ current time
diff --git a/yesod-core/yesod-core.cabal b/yesod-core/yesod-core.cabal
index 686e6e2a..ab2ffb8a 100644
--- a/yesod-core/yesod-core.cabal
+++ b/yesod-core/yesod-core.cabal
@@ -40,7 +40,7 @@ library
                    , shakespeare-css           >= 0.10     && < 0.11
                    , blaze-builder             >= 0.2.1    && < 0.4
                    , transformers              >= 0.2      && < 0.3
-                   , clientsession             >= 0.6      && < 0.7
+                   , clientsession             >= 0.7      && < 0.8
                    , random                    >= 1.0.0.2  && < 1.1
                    , cereal                    >= 0.2      && < 0.4
                    , old-locale                >= 1.0.0.2  && < 1.1