diff --git a/kernel/typeops.ml b/kernel/typeops.ml
index 2be97c4ada4da..c293b2a9a8e8d 100644
--- a/kernel/typeops.ml
+++ b/kernel/typeops.ml
@@ -661,7 +661,13 @@ module HConstr : sig
   (* May not be used on Rel! (subterms can be rels) *)
   val of_kind_nohashcons : (t,t,Sorts.t,UVars.Instance.t,Sorts.relevance) kind_of_term -> t
 
-  module Tbl : Hashtbl.S with type key = t
+  module Tbl : sig
+    type key = t
+    type 'a t
+    val find_opt : 'a t -> key -> 'a option
+    val add : 'a t -> key -> 'a -> unit
+    val create : int -> 'a t
+  end
 
 end = struct
 
@@ -775,7 +781,52 @@ let push_rel env =
     cnt = env.cnt;
   }
 
-module Tbl = Hashtbl.Make(Self)
+module Tbl = struct
+  type key = t
+
+  type 'a t = (key * 'a) list Int.Map.t ref
+
+  let create _ = ref Int.Map.empty
+
+  let add tbl key v =
+    tbl := Int.Map.update key.hash (function
+        | None -> Some [(key,v)]
+        | Some l -> Some ((key,v)::l))
+        !tbl
+
+  let find_opt tbl key =
+    match Int.Map.find_opt key.hash !tbl with
+    | None -> None
+    | Some l ->
+      List.find_map (fun (k',v) ->
+          if equal key k' then Some v else None)
+        l
+
+  type stats = {
+    hashes : int;
+    bindings : int;
+    most_collisions : int;
+  }
+
+  let empty_stats = {
+    hashes = 0;
+    bindings = 0;
+    most_collisions = 0;
+  }
+
+  let stats tbl =
+    Int.Map.fold (fun _ l acc ->
+        let len = List.length l in
+        {
+          hashes = acc.hashes + 1;
+          bindings = acc.bindings + len;
+          most_collisions = max acc.most_collisions len;
+        }
+      )
+      !tbl
+      empty_stats
+
+end
 
 let hash_annot = hash_annot Name.hash
 
@@ -971,12 +1022,11 @@ let of_constr env c =
   let tbl = Tbl.create 57 in
   let c = of_constr tbl local_env c in
   dbg Pp.(fun () ->
-      let open Hashtbl in
       let stats = Tbl.stats tbl in
       v 0 (
-        str "num_bindings = " ++ int stats.num_bindings ++ spc() ++
-        str "num_buckets = " ++ int stats.num_buckets ++ spc() ++
-        str "max_bucket_length = " ++ int stats.max_bucket_length
+        str "hashes = " ++ int stats.Tbl.hashes ++ spc() ++
+        str "bindings = " ++ int stats.Tbl.bindings ++ spc() ++
+        str "most_collisions = " ++ int stats.Tbl.most_collisions
     )
     );
   c