diff --git a/Data/ByteString/Internal.hs b/Data/ByteString/Internal.hs
index 4f8050ba4..4587d26ea 100644
--- a/Data/ByteString/Internal.hs
+++ b/Data/ByteString/Internal.hs
@@ -38,10 +38,12 @@ module Data.ByteString.Internal (
         -- * Low level imperative construction
         create,                 -- :: Int -> (Ptr Word8 -> IO ()) -> IO ByteString
         createUptoN,            -- :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString
-        createAndTrim,          -- :: Int -> (Ptr Word8 -> IO Int) -> IO  ByteString
+        createUptoN',           -- :: Int -> (Ptr Word8 -> IO (Int, a)) -> IO (ByteString, a)
+        createAndTrim,          -- :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString
         createAndTrim',         -- :: Int -> (Ptr Word8 -> IO (Int, Int, a)) -> IO (ByteString, a)
-        unsafeCreate,           -- :: Int -> (Ptr Word8 -> IO ()) ->  ByteString
-        unsafeCreateUptoN,      -- :: Int -> (Ptr Word8 -> IO Int) ->  ByteString
+        unsafeCreate,           -- :: Int -> (Ptr Word8 -> IO ()) -> ByteString
+        unsafeCreateUptoN,      -- :: Int -> (Ptr Word8 -> IO Int) -> ByteString
+        unsafeCreateUptoN',     -- :: Int -> (Ptr Word8 -> IO (Int, a)) -> (ByteString, a)
         mallocByteString,       -- :: Int -> IO (ForeignPtr a)
 
         -- * Conversion to and from ForeignPtrs
@@ -371,11 +373,12 @@ unsafeCreateUptoN :: Int -> (Ptr Word8 -> IO Int) -> ByteString
 unsafeCreateUptoN l f = unsafeDupablePerformIO (createUptoN l f)
 {-# INLINE unsafeCreateUptoN #-}
 
+-- | @since 0.10.12.0
 unsafeCreateUptoN' :: Int -> (Ptr Word8 -> IO (Int, a)) -> (ByteString, a)
 unsafeCreateUptoN' l f = unsafeDupablePerformIO (createUptoN' l f)
 {-# INLINE unsafeCreateUptoN' #-}
 
--- | Create ByteString of size @l@ and use action @f@ to fill it's contents.
+-- | Create ByteString of size @l@ and use action @f@ to fill its contents.
 create :: Int -> (Ptr Word8 -> IO ()) -> IO ByteString
 create l f = do
     fp <- mallocByteString l
@@ -383,8 +386,9 @@ create l f = do
     return $! PS fp 0 l
 {-# INLINE create #-}
 
--- | Create ByteString of up to size size @l@ and use action @f@ to fill it's
--- contents which returns its true size.
+-- | Given a maximum size @l@ and an action @f@ that fills the 'ByteString'
+-- starting at the given 'Ptr' and returns the actual utilized length,
+-- @`createUpToN'` l f@ returns the filled 'ByteString'.
 createUptoN :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString
 createUptoN l f = do
     fp <- mallocByteString l
@@ -392,7 +396,10 @@ createUptoN l f = do
     assert (l' <= l) $ return $! PS fp 0 l'
 {-# INLINE createUptoN #-}
 
--- | Create ByteString of up to size @l@ and use action @f@ to fill it's contents which returns its true size.
+-- | Like 'createUpToN', but also returns an additional value created by the
+-- action.
+--
+-- @since 0.10.12.0
 createUptoN' :: Int -> (Ptr Word8 -> IO (Int, a)) -> IO (ByteString, a)
 createUptoN' l f = do
     fp <- mallocByteString l