diff --git a/lib/Ast.ml b/lib/Ast.ml
index 31a95ca8cc..522342075d 100644
--- a/lib/Ast.ml
+++ b/lib/Ast.ml
@@ -1220,12 +1220,18 @@ end = struct
     let check_bindings l =
       List.exists l ~f:(fun {pvb_pat; _} -> check_subpat pvb_pat)
     in
-    let check_function_param param =
+    let check_param_val (_, _, p) = p == pat in
+    let check_expr_function_param param =
       match param.pparam_desc with
-      | `Param_val (_, _, p) -> p == pat
-      | `Param_newtype _ -> false
+      | Param_val x -> check_param_val x
+      | Param_newtype _ -> false
+    in
+    let check_class_function_param param =
+      check_param_val param.pparam_desc
+    in
+    let check_class_function_params =
+      List.exists ~f:check_class_function_param
     in
-    let check_function_params l = List.exists l ~f:check_function_param in
     match ctx with
     | Pld (PPat (p1, _)) -> assert (p1 == pat)
     | Pld _ -> assert false
@@ -1283,9 +1289,9 @@ end = struct
               | {pc_lhs; _} when pc_lhs == pat -> true
               | _ -> false ) )
       | Pexp_for (p, _, _, _, _) -> assert (p == pat)
-      | Pexp_fun (p, _) -> assert (check_function_param p) )
-    | Fpe ctx -> assert (check_function_param ctx)
-    | Fpc ctx -> assert (check_function_param ctx)
+      | Pexp_fun (p, _) -> assert (check_expr_function_param p) )
+    | Fpe ctx -> assert (check_expr_function_param ctx)
+    | Fpc ctx -> assert (check_class_function_param ctx)
     | Vc _ -> assert false
     | Lb x -> assert (x.pvb_pat == pat)
     | Bo x -> assert (x.pbop_pat == pat)
@@ -1294,7 +1300,7 @@ end = struct
     | Cl ctx ->
         assert (
           match ctx.pcl_desc with
-          | Pcl_fun (p, _) -> check_function_params p
+          | Pcl_fun (p, _) -> check_class_function_params p
           | Pcl_constr _ -> false
           | Pcl_structure {pcstr_self; _} ->
               Option.exists ~f:(fun self_ -> self_ == pat) pcstr_self
@@ -1336,12 +1342,18 @@ end = struct
       | PStr [{pstr_desc= Pstr_eval (e, _); _}] -> e == exp
       | _ -> false
     in
-    let check_function_param param =
+    let check_param_val (_, e, _) = Option.exists e ~f:(fun x -> x == exp) in
+    let check_expr_function_param param =
       match param.pparam_desc with
-      | `Param_val (_, e, _) -> Option.exists e ~f:(fun x -> x == exp)
-      | `Param_newtype _ -> false
+      | Param_val x -> check_param_val x
+      | Param_newtype _ -> false
+    in
+    let check_class_function_param param =
+      check_param_val param.pparam_desc
+    in
+    let check_class_function_params =
+      List.exists ~f:check_class_function_param
     in
-    let check_function_params l = List.exists l ~f:check_function_param in
     match ctx with
     | Pld (PPat (_, Some e1)) -> assert (e1 == exp)
     | Pld _ -> assert false
@@ -1371,7 +1383,7 @@ end = struct
                 | {pc_rhs; _} when pc_rhs == exp -> true
                 | _ -> false ) )
         | Pexp_fun (param, body) ->
-            assert (check_function_param param || body == exp)
+            assert (check_expr_function_param param || body == exp)
         | Pexp_indexop_access {pia_lhs; pia_kind= Builtin idx; pia_rhs; _} ->
             assert (
               pia_lhs == exp || idx == exp
@@ -1420,8 +1432,8 @@ end = struct
         | Pexp_for (_, e1, e2, _, e3) ->
             assert (e1 == exp || e2 == exp || e3 == exp)
         | Pexp_override e1N -> assert (List.exists e1N ~f:snd_f) )
-    | Fpe ctx -> assert (check_function_param ctx)
-    | Fpc ctx -> assert (check_function_param ctx)
+    | Fpe ctx -> assert (check_expr_function_param ctx)
+    | Fpc ctx -> assert (check_class_function_param ctx)
     | Vc _ -> assert false
     | Lb x -> assert (x.pvb_expr == exp)
     | Bo x -> assert (x.pbop_exp == exp)
@@ -1444,7 +1456,7 @@ end = struct
     | Cl ctx ->
         let rec loop ctx =
           match ctx.pcl_desc with
-          | Pcl_fun (param, e) -> check_function_params param || loop e
+          | Pcl_fun (param, e) -> check_class_function_params param || loop e
           | Pcl_constr _ -> false
           | Pcl_structure _ -> false
           | Pcl_apply (_, l) -> List.exists l ~f:(fun (_, e) -> e == exp)
@@ -1889,8 +1901,8 @@ end = struct
       | Ppat_cons _ -> true
       | Ppat_construct _ | Ppat_record _ | Ppat_variant _ -> false
       | _ -> true )
-    | Fpe {pparam_desc= `Param_val (_, _, _); _}, Ppat_cons _ -> true
-    | Fpc {pparam_desc= `Param_val (_, _, _); _}, Ppat_cons _ -> true
+    | Fpe {pparam_desc= Param_val (_, _, _); _}, Ppat_cons _ -> true
+    | Fpc {pparam_desc= _; _}, Ppat_cons _ -> true
     | Pat {ppat_desc= Ppat_construct _; _}, Ppat_cons _ -> true
     | _, Ppat_constraint (_, {ptyp_desc= Ptyp_poly _; _}) -> false
     | ( Exp {pexp_desc= Pexp_letop _; _}
diff --git a/lib/Extended_ast.ml b/lib/Extended_ast.ml
index 75ca950687..307543a223 100644
--- a/lib/Extended_ast.ml
+++ b/lib/Extended_ast.ml
@@ -235,18 +235,18 @@ module Parse = struct
           {p with pexp_desc= Pexp_pack (name, Some pt)}
       | { pexp_desc=
             Pexp_fun
-              ({pparam_desc= `Param_newtype types1; pparam_loc= loc1}, e1)
+              ({pparam_desc= Param_newtype types1; pparam_loc= loc1}, e1)
         ; pexp_attributes= []
         ; _ } as e ->
           let e =
             match (expr m e1).pexp_desc with
             | Pexp_fun
-                ({pparam_desc= `Param_newtype types2; pparam_loc= loc2}, e2)
+                ({pparam_desc= Param_newtype types2; pparam_loc= loc2}, e2)
               ->
                 { e with
                   pexp_desc=
                     Pexp_fun
-                      ( { pparam_desc= `Param_newtype (types1 @ types2)
+                      ( { pparam_desc= Param_newtype (types1 @ types2)
                         ; pparam_loc= {loc1 with loc_end= loc2.loc_end} }
                       , e2 ) }
             | _ -> e
diff --git a/lib/Fmt_ast.ml b/lib/Fmt_ast.ml
index 82785864ef..d39a838cfb 100644
--- a/lib/Fmt_ast.ml
+++ b/lib/Fmt_ast.ml
@@ -726,7 +726,7 @@ and type_constr_and_body c xbody =
       let exp_ctx =
         let pat = Ast_helper.Pat.any () in
         let param =
-          { pparam_desc= `Param_val (Nolabel, None, pat)
+          { pparam_desc= Param_val (Nolabel, None, pat)
           ; pparam_loc= pat.ppat_loc }
         in
         Exp Ast_helper.(Exp.fun_ param exp)
@@ -1342,13 +1342,12 @@ and fmt_expr_fun_arg c fp =
   Cmts.fmt c fp.pparam_loc
   @@
   match fp.pparam_desc with
-  | `Param_val x -> fmt_param_val c ctx x
-  | `Param_newtype x -> fmt_param_newtype c x
+  | Param_val x -> fmt_param_val c ctx x
+  | Param_newtype x -> fmt_param_newtype c x
 
 and fmt_class_fun_arg c fp =
   let ctx = Fpc fp in
-  Cmts.fmt c fp.pparam_loc
-  @@ match fp.pparam_desc with `Param_val x -> fmt_param_val c ctx x
+  Cmts.fmt c fp.pparam_loc @@ fmt_param_val c ctx fp.pparam_desc
 
 and fmt_expr_fun_args c args = list args "@;" (fmt_expr_fun_arg c)
 
diff --git a/lib/Sugar.ml b/lib/Sugar.ml
index 0c82ffb31a..3706d968a8 100644
--- a/lib/Sugar.ml
+++ b/lib/Sugar.ml
@@ -163,7 +163,7 @@ module Let_binding = struct
              [Extended_ast]. *)
           let pat = Ast_helper.Pat.any () in
           let param =
-            { pparam_desc= `Param_val (Nolabel, None, pat)
+            { pparam_desc= Param_val (Nolabel, None, pat)
             ; pparam_loc= pat.ppat_loc }
           in
           Exp (Ast_helper.Exp.fun_ param exp)
diff --git a/vendor/parser-extended/ast_mapper.ml b/vendor/parser-extended/ast_mapper.ml
index f81e954488..dcbb16dcf0 100644
--- a/vendor/parser-extended/ast_mapper.ml
+++ b/vendor/parser-extended/ast_mapper.ml
@@ -122,11 +122,10 @@ module FP = struct
     List.map (map_loc sub) ty
 
   let map_expr sub = function
-    | `Param_val x -> `Param_val (map_param_val sub x)
-    | `Param_newtype x -> `Param_newtype (map_param_newtype sub x)
+    | Param_val x -> Param_val (map_param_val sub x)
+    | Param_newtype x -> Param_newtype (map_param_newtype sub x)
 
-  let map_class sub = function
-    | `Param_val x -> `Param_val (map_param_val sub x)
+  let map_class sub x = map_param_val sub x
 
   let map sub f { pparam_loc; pparam_desc } =
     let pparam_loc = sub.location sub pparam_loc in
diff --git a/vendor/parser-extended/parser.mly b/vendor/parser-extended/parser.mly
index 5609f88eef..0feb64340e 100644
--- a/vendor/parser-extended/parser.mly
+++ b/vendor/parser-extended/parser.mly
@@ -2601,13 +2601,13 @@ param_newtype:
 ;
 expr_fun_param:
   mkfunparam(
-      param_val { `Param_val $1 }
-    | param_newtype { `Param_newtype $1 }
+      param_val { Param_val $1 }
+    | param_newtype { Param_newtype $1 }
   ) { $1 }
 ;
 class_fun_param:
   mkfunparam (
-    param_val { `Param_val $1 }
+    param_val { $1 }
   ) { $1 }
 ;
 fun_def:
diff --git a/vendor/parser-extended/parsetree.mli b/vendor/parser-extended/parsetree.mli
index 4a8c269682..af612dcae1 100644
--- a/vendor/parser-extended/parsetree.mli
+++ b/vendor/parser-extended/parsetree.mli
@@ -506,10 +506,13 @@ and 'a function_param =
     pparam_desc : 'a;
   }
 
-and expr_function_param =
-  [ `Param_val of param_val | `Param_newtype of param_newtype ] function_param
+and param_val_or_newtype =
+  | Param_val of param_val
+  | Param_newtype of param_newtype
 
-and class_function_param = [ `Param_val of param_val ] function_param
+and expr_function_param = param_val_or_newtype function_param
+
+and class_function_param = param_val function_param
 
 and type_constraint =
   | Pconstraint of core_type
diff --git a/vendor/parser-extended/printast.ml b/vendor/parser-extended/printast.ml
index e494118afe..7ce7ee1848 100644
--- a/vendor/parser-extended/printast.ml
+++ b/vendor/parser-extended/printast.ml
@@ -525,13 +525,12 @@ and param_newtype i ppf ty =
 and expr_function_param i ppf { pparam_desc = desc; pparam_loc = loc } =
   line i ppf "function_param %a\n" fmt_location loc;
   match desc with
-  | `Param_val x -> param_val i ppf x
-  | `Param_newtype x -> param_newtype i ppf x
+  | Param_val x -> param_val i ppf x
+  | Param_newtype x -> param_newtype i ppf x
 
 and class_function_param i ppf { pparam_desc = desc; pparam_loc = loc } =
   line i ppf "function_param %a\n" fmt_location loc;
-  match desc with
-  | `Param_val x -> param_val i ppf x
+  param_val i ppf desc
 
 and type_constraint i ppf constraint_ =
   match constraint_ with