diff --git a/Data/ByteString/Internal/Type.hs b/Data/ByteString/Internal/Type.hs
index f43e983ac..67c187e3e 100644
--- a/Data/ByteString/Internal/Type.hs
+++ b/Data/ByteString/Internal/Type.hs
@@ -137,6 +137,8 @@ import Foreign.Marshal.Utils
 
 #if PURE_HASKELL
 import qualified Data.ByteString.Internal.Pure as Pure
+import Data.Bits                (toIntegralSized, Bits)
+import Data.Maybe               (fromMaybe)
 #endif
 
 #if !MIN_VERSION_base(4,13,0)
@@ -1220,44 +1222,44 @@ foreign import ccall safe "bytestring_is_valid_utf8" cIsValidUtf8Safe
 
 -- | Reverse n-bytes from the second pointer into the first
 c_reverse :: Ptr Word8 -> Ptr Word8 -> CSize -> IO ()
-c_reverse p1 p2 sz = Pure.reverseBytes p1 p2 (fromIntegral sz)
+c_reverse p1 p2 sz = Pure.reverseBytes p1 p2 (checkedCast sz)
 
 -- | find maximum char in a packed string
 c_maximum :: Ptr Word8 -> CSize -> IO Word8
-c_maximum ptr sz = Pure.findMaximum ptr (fromIntegral sz)
+c_maximum ptr sz = Pure.findMaximum ptr (checkedCast sz)
 
 -- | find minimum char in a packed string
 c_minimum :: Ptr Word8 -> CSize -> IO Word8
-c_minimum ptr sz = Pure.findMinimum ptr (fromIntegral sz)
+c_minimum ptr sz = Pure.findMinimum ptr (checkedCast sz)
 
 -- | count the number of occurrences of a char in a string
 c_count :: Ptr Word8 -> CSize -> Word8 -> IO CSize
-c_count ptr sz c = fromIntegral <$> Pure.countOcc ptr (fromIntegral sz) c
+c_count ptr sz c = checkedCast <$> Pure.countOcc ptr (checkedCast sz) c
 
 -- | count the number of occurrences of a char in a string
 c_count_ba :: ByteArray# -> Int -> Word8 -> IO CSize
-c_count_ba ba o c = fromIntegral <$> Pure.countOccBA ba o c
+c_count_ba ba o c = checkedCast <$> Pure.countOccBA ba o c
 
 -- | duplicate a string, interspersing the character through the elements of the
 -- duplicated string
 c_intersperse :: Ptr Word8 -> Ptr Word8 -> CSize -> Word8 -> IO ()
-c_intersperse p1 p2 sz e = Pure.intersperse p1 p2 (fromIntegral sz) e
+c_intersperse p1 p2 sz e = Pure.intersperse p1 p2 (checkedCast sz) e
 
 -- | Quick sort bytes
 c_sort :: Ptr Word8 -> CSize -> IO ()
-c_sort ptr sz = Pure.quickSort ptr (fromIntegral sz)
+c_sort ptr sz = Pure.quickSort ptr (checkedCast sz)
 
 c_elem_index :: ByteArray# -> Word8 -> CSize -> IO CPtrdiff
-c_elem_index ba e sz = fromIntegral <$> Pure.elemIndex ba e (fromIntegral sz)
+c_elem_index ba e sz = checkedCast <$> Pure.elemIndex ba e (checkedCast sz)
 
 cIsValidUtf8BA :: ByteArray# -> CSize -> IO CInt
-cIsValidUtf8BA ba sz = bool_to_cint <$> Pure.isValidUtf8BA ba (fromIntegral sz)
+cIsValidUtf8BA ba sz = bool_to_cint <$> Pure.isValidUtf8BA ba (checkedCast sz)
 
 cIsValidUtf8BASafe :: ByteArray# -> CSize -> IO CInt
 cIsValidUtf8BASafe = cIsValidUtf8BA
 
 cIsValidUtf8 :: Ptr Word8 -> CSize -> IO CInt
-cIsValidUtf8 ptr sz = bool_to_cint <$> Pure.isValidUtf8 ptr (fromIntegral sz)
+cIsValidUtf8 ptr sz = bool_to_cint <$> Pure.isValidUtf8 ptr (checkedCast sz)
 
 cIsValidUtf8Safe :: Ptr Word8 -> CSize -> IO CInt
 cIsValidUtf8Safe = cIsValidUtf8
@@ -1266,6 +1268,11 @@ bool_to_cint :: Bool -> CInt
 bool_to_cint True = 1
 bool_to_cint False = 0
 
+checkedCast :: (Bits a, Bits b, Integral a, Integral b) => a -> b
+checkedCast x =
+  fromMaybe (errorWithoutStackTrace "checkedCast: overflow")
+            (toIntegralSized x)
+
 ----------------------------------------------------------------
 -- Haskell version of functions in itoa.c
 ----------------------------------------------------------------