diff --git a/src/Simplex/Chat/Mobile/Shared.hs b/src/Simplex/Chat/Mobile/Shared.hs
index d0c5b0b86e..d1f60ffce5 100644
--- a/src/Simplex/Chat/Mobile/Shared.hs
+++ b/src/Simplex/Chat/Mobile/Shared.hs
@@ -16,12 +16,12 @@ type JSONByteString = LB.ByteString
 getByteString :: Ptr Word8 -> CInt -> IO ByteString
 getByteString ptr len = do
   fp <- newForeignPtr_ ptr
-  pure $ BS fp $ fromIntegral len
+  pure $ PS fp 0 $ fromIntegral len
 {-# INLINE getByteString #-}
 
 putByteString :: Ptr Word8 -> ByteString -> IO ()
-putByteString ptr (BS fp len) =
-  withForeignPtr fp $ \p -> memcpy ptr p len
+putByteString ptr (PS fp offset len) =
+  withForeignPtr fp $ \p -> memcpy ptr (p `plusPtr` offset) len
 {-# INLINE putByteString #-}
 
 putLazyByteString :: Ptr Word8 -> LB.ByteString -> IO ()