diff --git a/src/Network/Wai/Middleware/Cache/Redis.hs b/src/Network/Wai/Middleware/Cache/Redis.hs
--- a/src/Network/Wai/Middleware/Cache/Redis.hs
+++ b/src/Network/Wai/Middleware/Cache/Redis.hs
@@ -23,7 +23,6 @@
     redisBackend,
 ) where
 
-import Control.Monad (void)
 import Control.Monad.IO.Class (liftIO)
 import qualified Control.Arrow as A (first)
 
@@ -53,8 +52,8 @@
     -> ByteString
             -- ^ Cache prefix for key and tags.  
             --   See "Database.Redis.Pile" for details.
-    -> Maybe Integer
-            -- ^ Cache TTL. Use 'Nothing' for no expiration.
+    -> Integer
+            -- ^ Cache TTL. Use @Zero (0)@  for no expiration.
     -> [ByteString]
             -- ^ Cache Tags. See "Database.Redis.Pile" for details.
     -> (Request -> ByteString)
@@ -65,15 +64,15 @@
             --   @304@-responses.
     -> CacheBackend
 redisBackend cInfo db cachePrefix ttl tags keyFn eTagFn app req = do
-    rawRes <- liftIO $ do
+    cachedResponse <- liftIO $ do
         conn <- R.connect cInfo
         R.runRedis conn $ do
-            void $ R.select db
+            _ <- R.select db
             pile cachePrefix key eTag $ liftIO . runResourceT $ do
                 res <- app req
                 (h, d) <- buildCachedResponse res
                 return (d, h, tags, ttl)
-    parseCachedResponse rawRes
+    parseCachedResponse cachedResponse
   where
     (key, eTag) = (keyFn req, eTagFn req)
 
diff --git a/wai-middleware-cache-redis.cabal b/wai-middleware-cache-redis.cabal
--- a/wai-middleware-cache-redis.cabal
+++ b/wai-middleware-cache-redis.cabal
@@ -1,5 +1,5 @@
 name:           wai-middleware-cache-redis
-version:        0.3.0
+version:        0.4.0
 cabal-version:  >= 1.8
 build-type:     Simple
 stability:      Experimental
@@ -25,8 +25,8 @@
                    bytestring >= 0.9 && < 0.10,
                    case-insensitive >= 0.2,
                    conduit >= 0.4 && < 0.5,
-                   hedis >= 0.4 && < 0.5,
-                   hedis-pile >= 0.5.1,
+                   hedis >= 0.5 && < 0.6,
+                   hedis-pile >= 0.6,
                    http-types >= 0.6 && < 0.7,
                    transformers >= 0.2 && < 0.4,
                    wai >= 1.2,