compiled heist not working?

default.tpl

<apply template="thingo">
  <hello/>
</apply>

Main.hs

{-# LANGUAGE OverloadedStrings #-}
import           Blaze.ByteString.Builder
import           Control.Lens
import           Control.Monad.Trans.Either
import qualified Data.ByteString            as B
import           Data.Map.Syntax
import           Heist
import           Heist.Compiled

main = do
  let hc = emptyHeistConfig
           & hcTemplateLocations .~ [loadTemplates "."]
           & hcCompiledSplices .~ do
             "hello" ## return (yieldPureText "aaaaaaaaa")
  hs      <- either (error "oops") id `fmap` runEitherT (initHeist hc)
  builder <- maybe  (error "oops") fst (renderTemplate hs "default")
  toByteStringIO B.putStr builder

stdout

<apply template='thingo'>
  <hello></hello>
</apply>&#10;

thingo.tpl

<div class="foob">
  <p> asdf hdg jsdg jsdgb </p>
  <apply-content/>
</div>