diff --git a/src/core-logic/term.ml b/src/core-logic/term.ml
index 2c0330eb..cf9f06f6 100644
--- a/src/core-logic/term.ml
+++ b/src/core-logic/term.ml
@@ -157,10 +157,10 @@ module Store = struct
   (* TODO: use atomic? CCAtomic? *)
   let n = ref 0
 
-  let create () : t =
+  let create ?(size = 256) () : t =
     let s_uid = !n in
     incr n;
-    { s_uid; s_exprs = Hcons.create ~size:256 () }
+    { s_uid; s_exprs = Hcons.create ~size () }
 
   (* check that [e] belongs in this store *)
   let[@inline] check_e_uid (self : t) (e : term) =
diff --git a/src/core-logic/term.mli b/src/core-logic/term.mli
index dfb2a65f..66e3e93b 100644
--- a/src/core-logic/term.mli
+++ b/src/core-logic/term.mli
@@ -99,7 +99,7 @@ val ty : t -> t
 module Store : sig
   type t = store
 
-  val create : unit -> t
+  val create : ?size:int -> unit -> t
 end
 
 val type_ : store -> t