diff --git spamoracle/mail.ml spamoracle/mail.ml

index 92d46e7..742771e 100644

--- spamoracle/mail.ml

+++ spamoracle/mail.ml

@@ -188,7 +188,7 @@ let run_body_through_external_converter cmd arg body =

     None

   end else begin

     let len = in_channel_length ic in

-    let res = String.create len in

+    let res = Bytes.create len in

     really_input ic res 0 len;

     close_in ic;

     safe_remove infile; safe_remove outfile;