diff --git a/Spock.cabal b/Spock.cabal
--- a/Spock.cabal
+++ b/Spock.cabal
@@ -1,5 +1,5 @@
 name:                Spock
-version:             0.4.3.0
+version:             0.4.3.1
 synopsis:            Another Haskell web toolkit based on scotty
 description:         This toolbox provides everything you need to get a quick start into web hacking with haskell: sessions, cookies, database helper, global state and the power of scotty
 Homepage:            https://github.com/agrafix/Spock
@@ -38,11 +38,11 @@
                        transformers ==0.3.*,
                        transformers-base ==0.4.*,
                        xsd ==0.4.*,
-                       aeson >=0.6,
                        resource-pool ==0.2.*,
                        random ==1.*,
                        pool-conduit ==0.1.*,
-                       vault ==0.3.*
+                       vault ==0.3.*,
+                       path-pieces ==0.1.*
   ghc-options: -Wall -fno-warn-orphans
 
 source-repository head
diff --git a/Web/Spock.hs b/Web/Spock.hs
--- a/Web/Spock.hs
+++ b/Web/Spock.hs
@@ -24,6 +24,8 @@
     , text, html, file, json, source, raw
     , raise, rescue, next
     , RoutePattern
+      -- * Spock utilities
+    , paramPathPiece
       -- * Internals for extending Spock
     , getSpockHeart, runSpockIO, WebStateM, WebState
     )
@@ -39,7 +41,9 @@
 import Control.Monad.Trans.Resource
 import Data.Pool
 import Web.Scotty.Trans
+import Web.PathPieces
 import qualified Network.HTTP.Types as Http
+import qualified Data.Text.Lazy as TL
 
 -- | Run a spock application using the warp server, a given db storageLayer and an initial state.
 -- Spock works with database libraries that already implement connection pooling and
@@ -89,3 +93,13 @@
 readSession =
     do mgr <- getSessMgr
        sm_readSession mgr
+
+-- | Same as "param", but the target type needs to implement "PathPiece"
+paramPathPiece :: PathPiece s => TL.Text -> SpockAction conn sess st s
+paramPathPiece t =
+    do val <- param t
+       case fromPathPiece val of
+         Just x ->
+             return x
+         Nothing ->
+             raise $ stringError $ "Cannot convert param: " ++ TL.unpack t ++ " to path piece!"