diff --git a/pkgs/development/ocaml-modules/httpun-ws/default.nix b/pkgs/development/ocaml-modules/httpun-ws/default.nix
index 0e199d7168e7..7cea73e84fb8 100644
--- a/pkgs/development/ocaml-modules/httpun-ws/default.nix
+++ b/pkgs/development/ocaml-modules/httpun-ws/default.nix
@@ -11,12 +11,12 @@
   alcotest,
 }:
 
-buildDunePackage rec {
+buildDunePackage (finalAttrs: {
   pname = "httpun-ws";
   version = "0.2.0";
 
   src = fetchurl {
-    url = "https://github.com/anmonteiro/httpun-ws/releases/download/${version}/httpun-ws-${version}.tbz";
+    url = "https://github.com/anmonteiro/httpun-ws/releases/download/${finalAttrs.version}/httpun-ws-${finalAttrs.version}.tbz";
     hash = "sha256-6uDNLg61tPyctthitxFqbw/IUDsuQ5BGvw5vTLLCl/0=";
   };
 
@@ -38,4 +38,4 @@ buildDunePackage rec {
     homepage = "https://github.com/anmonteiro/httpun-ws";
     maintainers = [ lib.maintainers.vbgl ];
   };
-}
+})