diff --git a/CHANGES b/CHANGES
index c9d1754..bf04719 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,7 @@
+unreleased
+========
+- #5: set minimum OCaml version
+
 1.0.1
 ========
 - #4: fix minimum ppxlib version
diff --git a/diff.opam b/diff.opam
index 34a67d1..c8b404a 100644
--- a/diff.opam
+++ b/diff.opam
@@ -9,6 +9,7 @@ homepage: "https://github.com/skolemlabs/diff"
 bug-reports: "https://github.com/skolemlabs/diff/issues"
 depends: [
   "dune" {>= "3.10"}
+  "ocaml" {>= "4.08.0"}
   "ppxlib" {>= "0.26.0"}
   "ocamlformat" {with-dev-setup}
   "ppx_deriving" {with-test}
diff --git a/dune-project b/dune-project
index f10feca..9bd4db4 100644
--- a/dune-project
+++ b/dune-project
@@ -15,6 +15,7 @@
  (name diff)
  (synopsis "A library for generating diffs from product types")
  (depends
+  (ocaml (>= 4.08.0))
   (ppxlib (>= 0.26.0))
   (ocamlformat :with-dev-setup)
   (ppx_deriving :with-test)