diff --git a/Concurrent-Cache.cabal b/Concurrent-Cache.cabal
--- a/Concurrent-Cache.cabal
+++ b/Concurrent-Cache.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                Concurrent-Cache
-version:             0.2.1.0
+version:             0.2.2.0
 synopsis:            A Cached variable for IO functions.
 description:         This package allows for caching IO functions, either on a
                      timeout or designed to only fetch once.
diff --git a/Control/Concurrent/Cache.hs b/Control/Concurrent/Cache.hs
--- a/Control/Concurrent/Cache.hs
+++ b/Control/Concurrent/Cache.hs
@@ -1,16 +1,16 @@
 module Control.Concurrent.Cache (CachedData, fetch, fetchCached, createReadOnceCache, createTimedCache) where
 
 import Data.Maybe (isNothing)
-import Control.Concurrent (forkIO, threadDelay, killThread, MVar, modifyMVar_, readMVar, ThreadId, newMVar)
+import Control.Concurrent (forkIO, threadDelay, killThread, MVar, modifyMVar_, readMVar, ThreadId, newMVar, mkWeakMVar)
+import System.Mem.Weak (deRefWeak, Weak)
 import Control.Monad (when, liftM)
 
 data Timeout = TimeSinceCreation Int | TimeSinceLastRead Int 
+type TimedCachedDataMVar a = MVar (Maybe ThreadId, IO a, Maybe a)
 
-data CachedData a = TimedCachedData (Timeout, (MVar (Maybe ThreadId, IO a, Maybe a))) | ReadOnceCachedData (MVar (Either (IO a) a))
+data CachedData a = TimedCachedData Timeout (TimedCachedDataMVar a) (Weak (TimedCachedDataMVar a)) | ReadOnceCachedData (MVar (Either (IO a) a))
 
--- |Only fetch data iff it has been cached. Useful for example when
--- a database connection is being cached, and it has to be closed when it
--- is no longer needed, but should not be opened just to be closed.
+-- |Only fetch data if it has been cached.
 fetchCached :: CachedData a
             -> IO (Maybe a)
 fetchCached (ReadOnceCachedData mvar) = do
@@ -19,11 +19,14 @@
                   Left _ -> Nothing
                   Right value -> Just value
 
-fetchCached (TimedCachedData (timeout, mvar)) = do
+fetchCached (TimedCachedData timeout mvar weakMVar) = do
   (_,_,value) <- readMVar mvar
   modifyMVar_ mvar $ \mvar'@(thread', action', value') -> do
     let newThread x = do threadDelay x
-                         modifyMVar_ mvar $ \(_, action'', _) -> return (Nothing, action'', Nothing)
+                         dereffed <- deRefWeak weakMVar
+                         case dereffed of
+                              Just mvar'' -> modifyMVar_ mvar'' $ \(_, action'', _) -> return (Nothing, action'', Nothing)
+                              Nothing -> return ()
     case timeout of
          TimeSinceLastRead time -> do
            when (not $ isNothing thread') $ let Just thread'' = thread' in killThread thread''
@@ -38,7 +41,6 @@
 
 -- |Fetch data from a cache
 fetch :: CachedData a
-      -- ^ @Cache@, the cache to fetch a value from
       -> IO (a)
 fetch state@(ReadOnceCachedData mvar) = go where
   go = do
@@ -51,7 +53,7 @@
         go
       Just value -> return value
 
-fetch state@(TimedCachedData (timeout, mvar)) = go where
+fetch state@(TimedCachedData timeout mvar _) = go where
   go = do
     cached <- fetchCached state
     case cached of
@@ -92,4 +94,5 @@
   let timeout' = if resetOnRead
                    then TimeSinceLastRead timeout
                    else TimeSinceCreation timeout
-  return $ TimedCachedData (timeout', var)
+  weakMVar <- mkWeakMVar var $ return ()
+  return $ TimedCachedData timeout' var weakMVar