diff --git a/pkgs/development/ocaml-modules/sedlex/default.nix b/pkgs/development/ocaml-modules/sedlex/default.nix
index 27756fdcd26..0ce962417ed 100644
--- a/pkgs/development/ocaml-modules/sedlex/default.nix
+++ b/pkgs/development/ocaml-modules/sedlex/default.nix
@@ -47,6 +47,7 @@ buildDunePackage rec {
   inherit (param) version;
 
   minimalOCamlVersion = "4.08";
+  duneVersion = "3";
 
   src = fetchFromGitHub {
     owner = "ocaml-community";