diff --git a/pkgs/development/ocaml-modules/multicore-magic/default.nix b/pkgs/development/ocaml-modules/multicore-magic/default.nix
index c8bd30b95544..cf724cc983b8 100644
--- a/pkgs/development/ocaml-modules/multicore-magic/default.nix
+++ b/pkgs/development/ocaml-modules/multicore-magic/default.nix
@@ -8,12 +8,12 @@
   js_of_ocaml,
 }:
 
-buildDunePackage rec {
+buildDunePackage (finalAttrs: {
   pname = "multicore-magic";
   version = "2.3.2";
 
   src = fetchurl {
-    url = "https://github.com/ocaml-multicore/multicore-magic/releases/download/${version}/multicore-magic-${version}.tbz";
+    url = "https://github.com/ocaml-multicore/multicore-magic/releases/download/${finalAttrs.version}/multicore-magic-${finalAttrs.version}.tbz";
     hash = "sha256-jY1wqCOq4c4EMDgIQqqIHErIONJFyvJ+0P8ld1CHF18=";
   };
 
@@ -34,4 +34,4 @@ buildDunePackage rec {
     homepage = "https://github.com/ocaml-multicore/multicore-magic";
     maintainers = [ lib.maintainers.vbgl ];
   };
-}
+})