diff --git a/overlays/default.nix b/overlays/default.nix
index 24e8e482..a5090cf1 100644
--- a/overlays/default.nix
+++ b/overlays/default.nix
@@ -33,9 +33,10 @@ with final; {
           url = "https://github.com/dexidp/dex/commit/000004b13b876e04a6f75ec0394f7cabe84fb15e.patch";
           hash = "sha256-u85RnwfhcQt7RK11Ed/fDLUbHOuD+TKJU8UHQslZowM=";
         });
-
-      vendorSha256 = lib.optionalString (ver == "2.35") "sha256-BxFiRHOGIJf3jTVtrw/QbnvG5gyfwAKQGd3IiWw5iVc="
-        + lib.optionalString (ver == "2.36") "sha256-hxq7JPz8uD5WQIPO2anSf9+kzyoQy/BQ0OVTblA8qts=";
+    } // lib.optionalAttrs (ver == "2.35") {
+      vendorSha256 = "sha256-BxFiRHOGIJf3jTVtrw/QbnvG5gyfwAKQGd3IiWw5iVc=";
+    } // lib.optionalAttrs (ver == "2.36") {
+      vendorHash = "sha256-hxq7JPz8uD5WQIPO2anSf9+kzyoQy/BQ0OVTblA8qts=";
     });
   };