diff --git a/Data/ByteString/Internal.hs b/Data/ByteString/Internal.hs
index c31cec086..4b98755fd 100644
--- a/Data/ByteString/Internal.hs
+++ b/Data/ByteString/Internal.hs
@@ -339,18 +339,18 @@ packChars cs = unsafePackLenChars (List.length cs) cs
  #-}
 
 unsafePackLenBytes :: Int -> [Word8] -> ByteString
-unsafePackLenBytes len xs0 =
-    unsafeCreate len $ \p -> go p xs0
-  where
-    go !_ []     = return ()
-    go !p (x:xs) = poke p x >> go (p `plusPtr` 1) xs
+unsafePackLenBytes len =
+    unsafeCreate len . foldr
+      (\x go p -> poke p x >> go (p `plusPtr` 1))
+      (\_ -> return ())
+{-# INLINE unsafePackLenBytes #-}
 
 unsafePackLenChars :: Int -> [Char] -> ByteString
-unsafePackLenChars len cs0 =
-    unsafeCreate len $ \p -> go p cs0
-  where
-    go !_ []     = return ()
-    go !p (c:cs) = poke p (c2w c) >> go (p `plusPtr` 1) cs
+unsafePackLenChars len =
+    unsafeCreate len . foldr
+      (\x go p -> poke p (c2w x) >> go (p `plusPtr` 1))
+      (\_ -> return ())
+{-# INLINE unsafePackLenChars #-}
 
 
 -- | /O(n)/ Pack a null-terminated sequence of bytes, pointed to by an
diff --git a/bench/BenchAll.hs b/bench/BenchAll.hs
index 451eebc65..641205124 100644
--- a/bench/BenchAll.hs
+++ b/bench/BenchAll.hs
@@ -23,6 +23,7 @@ import           Prelude                               hiding (words)
 
 import qualified Data.ByteString                       as S
 import qualified Data.ByteString.Char8                 as S8
+import qualified Data.ByteString.Internal              as SI
 import qualified Data.ByteString.Lazy                  as L
 import qualified Data.ByteString.Lazy.Char8            as L8
 
@@ -481,6 +482,18 @@ main = do
       [ bench "lazy"   $ nf L8.unlines (map (L8.pack . show) intData)
       , bench "strict" $ nf S8.unlines (map (S8.pack . show) intData)
       ]
+    , bgroup "pack"
+      [ bench "not fused" $ nf S.pack (replicate nRepl 0)
+      , bench "fused" $ nf (S.pack . replicate nRepl) 0
+      ]
+    , bgroup "unsafePackLenBytes"
+      [ bench "not fused" $ nf (SI.unsafePackLenBytes nRepl) (replicate nRepl 0)
+      , bench "fused" $ nf (SI.unsafePackLenBytes nRepl . replicate nRepl) 0
+      ]
+    , bgroup "unsafePackLenChar"
+      [ bench "not fused" $ nf (SI.unsafePackLenChars nRepl) (replicate nRepl 'A')
+      , bench "fused" $ nf (SI.unsafePackLenChars nRepl . replicate nRepl) 'A'
+      ]
     , benchBoundsCheckFusion
     , benchCount
     , benchCSV