--- a/fls/fls.ml 2021-04-26 16:24:25.363442099 +0200 +++ b/fls/fls.ml 2021-04-26 20:10:54.965405870 +0200 @@ -750,7 +750,7 @@ match input inp s 0 1024 with 0 -> Buffer.contents res | n -> - Buffer.add_substring res s 0 n; + Buffer.add_subbytes res s 0 n; fill_buff () in let s = fill_buff () in