diff --git a/pkgs/development/ocaml-modules/janestreet/0.15.nix b/pkgs/development/ocaml-modules/janestreet/0.15.nix
index e5422f3a925d..183a3ff43458 100644
--- a/pkgs/development/ocaml-modules/janestreet/0.15.nix
+++ b/pkgs/development/ocaml-modules/janestreet/0.15.nix
@@ -161,6 +161,7 @@ with self;
   };
 
   async_websocket = janePackage {
+    duneVersion = "3";
     pname = "async_websocket";
     hash = "16ixqfnx9jp77bvx11dlzsq0pzfpyiif60hl2q06zncyswky9xgb";
     meta.description = "A library that implements the websocket protocol on top of Async";