diff --git a/pkgs/by-name/ex/expat/package.nix b/pkgs/by-name/ex/expat/package.nix
index 72459e1c2ac6..2e831ef025da 100644
--- a/pkgs/by-name/ex/expat/package.nix
+++ b/pkgs/by-name/ex/expat/package.nix
@@ -18,17 +18,17 @@
 # files.
 
 let
-  version = "2.8.2";
-  tag = "R_${lib.replaceStrings [ "." ] [ "_" ] version}";
+  tagFor = version: "R_${lib.replaceStrings [ "." ] [ "_" ] version}";
 in
+
 stdenv.mkDerivation (finalAttrs: {
   pname = "expat";
-  inherit version;
+  version = "2.8.2";
 
   src = fetchurl {
     url =
       with finalAttrs;
-      "https://github.com/libexpat/libexpat/releases/download/${tag}/${pname}-${version}.tar.xz";
+      "https://github.com/libexpat/libexpat/releases/download/${tagFor version}/${pname}-${version}.tar.xz";
     hash = "sha256-OtibhYjmZEvU5JmBSA1IshKJ7rvNTwoaSvscKfmbarQ=";
   };
 
@@ -73,7 +73,7 @@ stdenv.mkDerivation (finalAttrs: {
   };
 
   meta = {
-    changelog = "https://github.com/libexpat/libexpat/blob/${tag}/expat/Changes";
+    changelog = "https://github.com/libexpat/libexpat/blob/${tagFor finalAttrs.version}/expat/Changes";
     homepage = "https://libexpat.github.io/";
     description = "Stream-oriented XML parser library written in C";
     mainProgram = "xmlwf";