diff --git a/src/ppx_typerep_conv.ml b/src/ppx_typerep_conv.ml
index 6e92817..15fa079 100644
--- a/src/ppx_typerep_conv.ml
+++ b/src/ppx_typerep_conv.ml
@@ -184,7 +184,7 @@ module Typerep_implementation = struct
 
     val arg_of_param : string -> string
 
-    val params_names : params:(core_type * variance) list -> string list
+    val params_names : params:(core_type * (variance * injectivity)) list -> string list
     val params_patts : loc:Location.t -> params_names:string list -> pattern list
 
     val type_name_module_definition : loc:Location.t -> path:string ->
@@ -233,7 +233,7 @@ module Typerep_implementation = struct
     let str_item_type_and_name ~loc ~path ~params_names ~type_name =
       let params =
         List.map params_names
-          ~f:(fun name -> (ptyp_var ~loc name, Invariant))
+          ~f:(fun name -> (ptyp_var ~loc name, (NoVariance, NoInjectivity)))
       in
       let td =
         let manifest =