diff --git a/dune b/dune
index b664be0..87f6af6 100644
--- a/dune
+++ b/dune
@@ -10,7 +10,6 @@
 (test
  (name rule110)
  (modules rule110)
- (enabled_if %{arch_sixtyfour})
  (libraries hashcons))
 
 (test
diff --git a/dune-project b/dune-project
index 3382b0d..d346151 100644
--- a/dune-project
+++ b/dune-project
@@ -1,2 +1,3 @@
 (lang dune 2.7)
 (name hashcons)
+(formatting (enabled_for dune))
diff --git a/hashcons.opam b/hashcons.opam
index 1b6d8ee..3c9d300 100644
--- a/hashcons.opam
+++ b/hashcons.opam
@@ -14,7 +14,7 @@ homepage: "https://github.com/backtracking/ocaml-hashcons"
 bug-reports: "https://github.com/backtracking/ocaml-hashcons/issues"
 depends: [
   "dune" {>= "2.7"}
-  "ocaml" {>= "4.07"}
+  "ocaml" {>= "4.12"}
   "odoc" {with-doc}
 ]
 build: [
diff --git a/rule110.ml b/rule110.ml
index 3ae2fec..2c953a2 100644
--- a/rule110.ml
+++ b/rule110.ml
@@ -196,13 +196,15 @@ let of_string s =
 
 (* a few tests *)
 
-let test s n b =
-  let c = of_string s in
-  let c = steps n c in
-  assert (bits c = b)
-let () = test "0000000000000000" 1 0
-let () = test "1111111111111111" 1 3
-let () = test "0010000001010100" 0 4
-let () = test "0100011101011100" 1000 595
-let () = test "1010100010111101" 1000000 591649
-let () = test "1010100010111101" 1152921504606846975 682111393702695301
+let test ?(size=32) s n b =
+  if Sys.word_size >= size then (
+    let c = of_string s in
+    let c = steps (int_of_string n) c in
+    assert (bits c = int_of_string b)
+  )
+let () = test "0000000000000000" "1" "0"
+let () = test "1111111111111111" "1" "3"
+let () = test "0010000001010100" "0" "4"
+let () = test "0100011101011100" "1000" "595"
+let () = test "1010100010111101" "1000000" "591649"
+let () = test ~size:64 "1010100010111101" "1152921504606846975" "682111393702695301"