diff --git a/pkgs/development/ocaml-modules/optint/default.nix b/pkgs/development/ocaml-modules/optint/default.nix
index 2726e0aae889..aa87256c746f 100644
--- a/pkgs/development/ocaml-modules/optint/default.nix
+++ b/pkgs/development/ocaml-modules/optint/default.nix
@@ -4,12 +4,12 @@
   fetchurl,
 }:
 
-buildDunePackage rec {
+buildDunePackage (finalAttrs: {
   minimalOCamlVersion = "4.07";
   version = "0.3.0";
   pname = "optint";
   src = fetchurl {
-    url = "https://github.com/mirage/optint/releases/download/v${version}/optint-${version}.tbz";
+    url = "https://github.com/mirage/optint/releases/download/v${finalAttrs.version}/optint-${finalAttrs.version}.tbz";
     sha256 = "sha256-KVz/LBNLA4WxO6gdUAXZ+EG6QNSlAq7RDJl/I57xFHs=";
   };
 
@@ -19,4 +19,4 @@ buildDunePackage rec {
     license = lib.licenses.mit;
     maintainers = [ lib.maintainers.vbgl ];
   };
-}
+})