diff --git a/ocaml/Block.ml b/ocaml/Block.ml
index 3a7ad79..0d84642 100644
--- a/ocaml/Block.ml
+++ b/ocaml/Block.ml
@@ -110,7 +110,9 @@ let read_bytes b idx =
        Bytes.get_int64_ne b idx
        |> Int64.to_int
      in
-     Some (Bytes.sub b (idx+8) m, idx+8+m)
+     try
+       Some (Bytes.sub b (idx+8) m, idx+8+m)
+     with Invalid_argument _ -> None