diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,7 @@
+0.5.1.0
+-------
+* Remove `Monoid w` constraint from MonadFork instances for RWS
+
 0.5.0.1
 -------
 * Support GHC 7.4.2
diff --git a/concurrent-state.cabal b/concurrent-state.cabal
--- a/concurrent-state.cabal
+++ b/concurrent-state.cabal
@@ -1,5 +1,5 @@
 name:                concurrent-state
-version:             0.5.0.1
+version:             0.5.1.0
 synopsis:            MTL-like library using TVars
 description:         State, RWS backed by TVar.
 homepage:            https://github.com/joelteon/concurrent-state
diff --git a/src/Control/Monad/RWS/Concurrent/Lazy.hs b/src/Control/Monad/RWS/Concurrent/Lazy.hs
--- a/src/Control/Monad/RWS/Concurrent/Lazy.hs
+++ b/src/Control/Monad/RWS/Concurrent/Lazy.hs
@@ -9,6 +9,7 @@
 -- Portability : portable
 --
 -- Concurrent RWS monad, combining a Reader, a Writer, and a State monad.
+--
 -- This module performs computations lazily. For a strict version, see
 -- "Control.Monad.RWS.Concurrent.Strict".
 -----------------------------------------------------------------------------
@@ -118,7 +119,7 @@
 
 instance (Monoid w, MonadIO m, MonadReader r m, MonadWriter w m, MonadState s m) => MonadRWS r w s (RWSC r w s m)
 
-instance (Monoid w, MonadFork m) => MonadFork (RWSC r w s m) where
+instance MonadFork m => MonadFork (RWSC r w s m) where
     fork = liftFork fork
     forkOn i = liftFork (forkOn i)
     forkOS = liftFork forkOS
diff --git a/src/Control/Monad/RWS/Concurrent/Strict.hs b/src/Control/Monad/RWS/Concurrent/Strict.hs
--- a/src/Control/Monad/RWS/Concurrent/Strict.hs
+++ b/src/Control/Monad/RWS/Concurrent/Strict.hs
@@ -9,7 +9,8 @@
 -- Portability : portable
 --
 -- Concurrent RWS monad, combining a Reader, a Writer, and a State monad.
--- This module performs computations strictly. For a strict version, see
+--
+-- This module performs computations strictly. For a lazy version, see
 -- "Control.Monad.RWS.Concurrent.Lazy".
 -----------------------------------------------------------------------------
 module Control.Monad.RWS.Concurrent.Strict (
@@ -118,7 +119,7 @@
 
 instance (Monoid w, MonadIO m, MonadReader r m, MonadWriter w m, MonadState s m) => MonadRWS r w s (RWSC r w s m)
 
-instance (Monoid w, MonadFork m) => MonadFork (RWSC r w s m) where
+instance MonadFork m => MonadFork (RWSC r w s m) where
     fork = liftFork fork
     forkOn i = liftFork (forkOn i)
     forkOS = liftFork forkOS