diff --git a/vendor/opam-file-format/opamLexer.mll b/vendor/opam-file-format/opamLexer.mll
index 26b0228af12..ac7db37650f 100644
--- a/vendor/opam-file-format/opamLexer.mll
+++ b/vendor/opam-file-format/opamLexer.mll
@@ -82,8 +82,7 @@ let char_for_hexadecimal_code lexbuf i =
   Char.chr (val1 * 16 + val2)
 
 (* Some hash-consing for strings *)
-module HS =
-  Weak.Make(struct include String let hash = Hashtbl.hash let equal = (=) end)
+module HS = Weak.Make(String)
 let hm = HS.create 317