diff --git a/ocamlbuild/flags.ml b/ocamlbuild/flags.ml
index c776953..89cecd7 100644
--- a/ocamlbuild/flags.ml
+++ b/ocamlbuild/flags.ml
@@ -27,6 +27,7 @@ let tags_of_decl { tags; _ } = tags
 let all_decls = ref []

 let of_tags matched_tags =
+  Param_tags.init ();
   S begin
     List.fold_left begin fun acc { tags; flags; _ } ->
       if Tags.does_match matched_tags tags then flags :: acc