diff --git a/Control/Monad/Reader/Class.hs b/Control/Monad/Reader/Class.hs
index 60f8383..c8b08ef 100644
--- a/Control/Monad/Reader/Class.hs
+++ b/Control/Monad/Reader/Class.hs
@@ -43,7 +43,7 @@ than using the 'Control.Monad.State.State' monad.
 
 module Control.Monad.Reader.Class (
     MonadReader(..),
-    asks,
+    asks, withEnv
     ) where
 
 import Control.Monad.Trans.Cont as Cont
@@ -98,6 +98,10 @@ asks :: MonadReader r m
     -> m a
 asks = reader
 
+-- | Executes a computation in a predefined environment.
+withEnv :: MonadReader r m => r -> m a -> m a
+withEnv env = local (const env)
+
 -- ----------------------------------------------------------------------------
 -- The partially applied function type is a simple reader monad