diff --git a/benches/bench.hs b/benches/bench.hs
--- a/benches/bench.hs
+++ b/benches/bench.hs
@@ -7,18 +7,18 @@
 main :: IO ()
 main = defaultMain
   [ bgroup "ArbByteString"
-    [ bench "arbitrary"    $ action (arbitrary :: Gen ArbByteString)
-    , bench "arbitrary1M"  $ action (arbitrary :: Gen ArbByteString1M)
-    , bench "arbitrary10M" $ action (arbitrary :: Gen ArbByteString10M)
+    [ bench "arbitrary"    $ nfIO $ action (arbitrary :: Gen ArbByteString)
+    , bench "arbitrary1M"  $ nfIO $ action (arbitrary :: Gen ArbByteString1M)
+    , bench "arbitrary10M" $ nfIO $ action (arbitrary :: Gen ArbByteString10M)
     , bgroup "fastRandBs"
-      [ bench "10B" $ action (fastRandBs 10)
-      , bench "1KB" $ action (fastRandBs 1024)
-      , bench "1MB" $ action (fastRandBs (1024*1024))
+      [ bench "10B" $ nfIO $ action (fastRandBs 10)
+      , bench "1KB" $ nfIO $ action (fastRandBs 1024)
+      , bench "1MB" $ nfIO $ action (fastRandBs (1024*1024))
       ]
     , bgroup "slowRandBs"
-      [ bench "10B" $ action (slowRandBs 10)
-      , bench "1KB" $ action (slowRandBs 1024)
-      , bench "10KB" $ action (slowRandBs 10240)
+      [ bench "10B" $ nfIO $ action (slowRandBs 10)
+      , bench "1KB" $ nfIO $ action (slowRandBs 1024)
+      , bench "10KB" $ nfIO $ action (slowRandBs 10240)
       ]
     ]
   ]
diff --git a/bytestring-arbitrary.cabal b/bytestring-arbitrary.cabal
--- a/bytestring-arbitrary.cabal
+++ b/bytestring-arbitrary.cabal
@@ -2,7 +2,7 @@
 --  documentation, see http://haskell.org/cabal/users-guide/
 
 name:                bytestring-arbitrary
-version:             0.0.3
+version:             0.0.4
 synopsis:            Arbitrary instances for ByteStrings
 -- description:         
 homepage:            https://github.com/tsuraan/bytestring-arbitrary
@@ -20,7 +20,7 @@
   exposed-modules:     Data.ByteString.Arbitrary
   -- other-modules:       
   -- other-extensions:    
-  build-depends:       base >=4.6 && <4.8
+  build-depends:       base >=4.6 && <4.9
                      , bytestring >=0.10 && <0.12
                      , cryptohash
                      , QuickCheck
@@ -32,7 +32,7 @@
   type:                exitcode-stdio-1.0
   hs-source-dirs:      benches
   main-is:             bench.hs
-  build-depends:       base >=4.6 && <4.8
+  build-depends:       base >=4.6 && <4.9
                      , bytestring >=0.10 && <0.12
                      , cryptohash
                      , QuickCheck