diff --git a/pkgs/development/ocaml-modules/mdx/default.nix b/pkgs/development/ocaml-modules/mdx/default.nix
index cd9cb2370d39..09f505c0e254 100644
--- a/pkgs/development/ocaml-modules/mdx/default.nix
+++ b/pkgs/development/ocaml-modules/mdx/default.nix
@@ -8,6 +8,8 @@ buildDunePackage rec {
   version = "2.1.0";
   useDune2 = true;
 
+  minimalOCamlVersion = "4.08";
+
   src = fetchurl {
     url = "https://github.com/realworldocaml/mdx/releases/download/${version}/mdx-${version}.tbz";
     sha256 = "sha256-ol1zy8LODDYdcnv/jByE0pnqJ5ujQuMALq3v9y7td/o=";
diff --git a/pkgs/development/ocaml-modules/printbox/default.nix b/pkgs/development/ocaml-modules/printbox/default.nix
index b42df087a9a6..179e559d72fe 100644
--- a/pkgs/development/ocaml-modules/printbox/default.nix
+++ b/pkgs/development/ocaml-modules/printbox/default.nix
@@ -17,8 +17,8 @@ buildDunePackage rec {
 
   checkInputs = [ mdx.bin ];
 
-  # mdx is not available for OCaml < 4.07
-  doCheck = lib.versionAtLeast ocaml.version "4.07";
+  # mdx is not available for OCaml < 4.08
+  doCheck = lib.versionAtLeast ocaml.version "4.08";
 
   meta = {
     homepage = "https://github.com/c-cube/printbox/";