diff --git a/pkgs/development/ocaml-modules/ocsigen-ppx-rpc/default.nix b/pkgs/development/ocaml-modules/ocsigen-ppx-rpc/default.nix
index 0db40c254bd..fdd6b91f19f 100644
--- a/pkgs/development/ocaml-modules/ocsigen-ppx-rpc/default.nix
+++ b/pkgs/development/ocaml-modules/ocsigen-ppx-rpc/default.nix
@@ -4,6 +4,8 @@ buildDunePackage rec {
   pname = "ocsigen-ppx-rpc";
   version = "1.0";
 
+  duneVersion = "3";
+
   src = fetchFromGitHub {
     owner = "ocsigen";
     repo = pname;