--- a/Control/Concurrent/ReadWriteLock/Test.hs
+++ b/Control/Concurrent/ReadWriteLock/Test.hs
@@ -97,7 +97,7 @@ test2 = assert $ within (10 * a_moment)
           RWLock.acquireRead rwl
 
 stressTest :: Assertion
-stressTest = assert $ within (500 * a_moment) $ do
+stressTest = assert $ within (1000 * a_moment) $ do
   lock <- RWLock.new
 
   let randomDelay hi = randomRIO (0, hi) >>= threadDelay
