diff --git a/src/data/CCHashconsedSet.ml b/src/data/CCHashconsedSet.ml
index b4e9e15e..7f9a2985 100644
--- a/src/data/CCHashconsedSet.ml
+++ b/src/data/CCHashconsedSet.ml
@@ -60,6 +60,9 @@ module type S = sig
   val compare : t -> t -> int
   (** Fast (arbitrary) comparisontest [O(1)] *)
 
+  val hash : t -> int
+  (** Fast (arbitrary, deterministic) hash [O(1)] *)
+
   val add : elt -> t -> t
 
   val remove : elt -> t -> t
@@ -207,6 +210,8 @@ module Make(E : ELT) : S with type elt = E.t = struct
 
   let compare t1 t2 = Pervasives.compare t1.id t2.id
 
+  let hash t = t.id land max_int
+
   let mem x t = mem_rec_ (E.hash x) x t
 
   let mk_node_ prefix switch l r = match l.cell, r.cell with
diff --git a/src/data/CCHashconsedSet.mli b/src/data/CCHashconsedSet.mli
index 2cc30ca4..a856d445 100644
--- a/src/data/CCHashconsedSet.mli
+++ b/src/data/CCHashconsedSet.mli
@@ -62,6 +62,9 @@ module type S = sig
   val compare : t -> t -> int
   (** Fast (arbitrary) comparisontest [O(1)] *)
 
+  val hash : t -> int
+  (** Fast (arbitrary, deterministic) hash [O(1)] *)
+
   val add : elt -> t -> t
 
   val remove : elt -> t -> t