Haskell Spock: How to get the raw request body

Question

The body function in Web.Spock.Action is supposed to return the raw request body. However, it just doesn't seem to be doing that:

{-# LANGUAGE OverloadedStrings #-}
module Main where

import Data.Text.Encoding (decodeUtf8)
import Debug.Trace        (trace)
import Web.Spock
import Web.Spock.Config

app :: SpockM () () () ()
app = do
    get root $ text "Hello!"
    post "test" $ do
        b <- body       -- b is always ""!
        text $ trace ("b="++show b) decodeUtf8 b

main :: IO ()
main = do
       spockCfg <- defaultSpockCfg () PCNoDatabase ()
       runSpock 3000 (spock spockCfg app)

A curl --data 123123 localhost:3000/test returns nothing, and the trace output confirms that b is an empty string.

Spock is running on port 3000
b=""

The equivalent Scotty app works just fine:

{-# LANGUAGE OverloadedStrings #-}
module Main where

import Data.Text.Lazy.Encoding (decodeUtf8)
import Web.Scotty

main = scotty 3000 $ do
    get "/" $ text "Hello!"
    post "/test" $  do
        b <- body       -- works fine
        text $ decodeUtf8 b

I absolutely can't see what I'm doing wrong. Any input would be highly appreciated!

Update: Above example will work with Spock >= 0.12.0.0!