diff --git a/pkgs/development/ocaml-modules/lru/default.nix b/pkgs/development/ocaml-modules/lru/default.nix
index 678023bb8f3..2c8a3e99df5 100644
--- a/pkgs/development/ocaml-modules/lru/default.nix
+++ b/pkgs/development/ocaml-modules/lru/default.nix
@@ -4,6 +4,8 @@ buildDunePackage rec {
   pname = "lru";
   version = "0.3.1";
 
+  duneVersion = "3";
+
   src = fetchurl {
     url = "https://github.com/pqwy/lru/releases/download/v${version}/lru-${version}.tbz";
     hash = "sha256-bL4j0np9WyRPhpwLiBQNR/cPQTpkYu81wACTJdSyNv0=";