diff --git a/src/System/Random/TF/Gen.hs b/src/System/Random/TF/Gen.hs
--- a/src/System/Random/TF/Gen.hs
+++ b/src/System/Random/TF/Gen.hs
@@ -1,4 +1,4 @@
-{-# Language BangPatterns, MagicHash, ForeignFunctionInterface, UnliftedFFITypes #-}
+{-# Language CPP, BangPatterns, MagicHash, ForeignFunctionInterface, UnliftedFFITypes #-}
 -- |
 -- Module    : System.Random.TF.Gen
 -- Copyright : (c) 2012-2013 Michał Pałka
@@ -17,7 +17,7 @@
 
 import qualified System.Random as R
 
-import System.IO.Unsafe ( unsafeDupablePerformIO )
+import System.IO.Unsafe
 
 import Data.Bits
 import Data.Char (toUpper, isSpace)
@@ -27,6 +27,11 @@
 import Data.Primitive.ByteArray
 
 import Numeric
+
+#if !MIN_VERSION_base(4,4,0)
+unsafeDupablePerformIO :: IO a -> a
+unsafeDupablePerformIO = unsafePerformIO
+#endif
 
 foreign import ccall unsafe "skein.h Threefish_256_Process_Block"
   threefish256EncryptBlock ::
diff --git a/src/System/Random/TF/Instances.hs b/src/System/Random/TF/Instances.hs
--- a/src/System/Random/TF/Instances.hs
+++ b/src/System/Random/TF/Instances.hs
@@ -1,4 +1,4 @@
-{-# Language BangPatterns, ScopedTypeVariables #-}
+{-# Language CPP, BangPatterns, ScopedTypeVariables #-}
 -- |
 -- Module    : System.Random.TF.Instances
 -- Copyright : (c) 2012-2013 Michał Pałka
@@ -21,6 +21,14 @@
 
 import System.Random.TF.Gen
 
+#if !MIN_VERSION_base(4,5,0)
+unsafeShiftR :: Bits a => a -> Int -> a
+unsafeShiftR = shiftR
+
+unsafeShiftL :: Bits a => a -> Int -> a
+unsafeShiftL = shiftL
+#endif
+
 myUnfoldr :: (t -> (a, t)) -> t -> [a]
 myUnfoldr f g = x' : myUnfoldr f g'
   where
@@ -66,6 +74,7 @@
 
 -- Inspired by Java's java.util.Random.
 -- This version avoids division modulo.
+-- Returns a random number from range [0..k-1], or from the full range if k = 0.
 {-# INLINE randomWord32' #-}
 randomWord32' :: RandomGen g => Word32 -> g -> (Word32, g)
 randomWord32' k
diff --git a/tf-random.cabal b/tf-random.cabal
--- a/tf-random.cabal
+++ b/tf-random.cabal
@@ -10,7 +10,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             0.1
+version:             0.2
 
 -- A short (one-line) description of the package.
 synopsis:            High-quality splittable pseudorandom number generator
@@ -86,7 +86,7 @@
 
   -- Other library packages from which modules are imported.
   build-depends:
-    base >= 4.5 && < 5,
+    base >= 4.2 && < 5,
     primitive >= 0.3,
     random >= 1.0.1.1,
     time