diff --git a/persistent-refs.cabal b/persistent-refs.cabal
--- a/persistent-refs.cabal
+++ b/persistent-refs.cabal
@@ -1,5 +1,5 @@
 name:                persistent-refs
-version:             0.3
+version:             0.4
 license:             BSD3
 license-file:        LICENSE
 author:              Adam C. Foltzer
@@ -26,7 +26,7 @@
   build-depends:     base         >= 4.0 && < 5,
                      containers   >= 0.4,
                      mtl          >= 2.1,
-                     ref-fd       >= 0.3,
+                     ref-fd       >= 0.3.0.4,
                      transformers >= 0.3
   exposed-modules:   Control.Monad.ST.Persistent,
                      Data.STRef.Persistent
diff --git a/src/Control/Monad/ST/Persistent/Internal.hs b/src/Control/Monad/ST/Persistent/Internal.hs
--- a/src/Control/Monad/ST/Persistent/Internal.hs
+++ b/src/Control/Monad/ST/Persistent/Internal.hs
@@ -1,14 +1,20 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE Rank2Types #-}
 
 module Control.Monad.ST.Persistent.Internal where
 
-import Control.Applicative (Alternative, Applicative)
 import Control.Monad.State.Strict
 import Data.Functor.Identity
 import Data.IntMap (IntMap, empty)
 import GHC.Base (Any)
 
+#if MIN_VERSION_base(4,8,0)
+import Control.Applicative (Alternative)
+#else
+import Control.Applicative (Alternative, Applicative)
+#endif
+
 data Heap = Heap { heap :: IntMap Any, next :: Int }
 
 emptyHeap :: Heap
@@ -21,7 +27,7 @@
 -- pure value. The rank-2 type offers similar guarantees to
 -- 'Control.Monad.ST.runST'.
 runST :: (forall s. ST s a) -> a
-runST = runIdentity . runSTT
+runST m = runIdentity (runSTT m)
 
 newtype STT s m a = STT (StateT Heap m a)
     deriving (Functor, Applicative, Alternative, Monad, MonadIO, MonadPlus, MonadTrans)
diff --git a/src/Data/STRef/Persistent.hs b/src/Data/STRef/Persistent.hs
--- a/src/Data/STRef/Persistent.hs
+++ b/src/Data/STRef/Persistent.hs
@@ -23,7 +23,6 @@
   , asInt
     -- * 'MonadRef' Operations
   , MonadRef(..)
-  , modifyRef'
   ) where
 
 import Control.Monad.State
@@ -63,9 +62,3 @@
     newRef   = newSTRef
     readRef  = readSTRef
     writeRef = writeSTRef
-
-modifyRef' :: MonadRef r m => r a -> (a -> a) -> m ()
-modifyRef' r f = do
-    x <- readRef r
-    let x' = f x
-    x' `seq` writeRef r x'