diff --git a/overlays/default.nix b/overlays/default.nix
index 4d92b75..ccea795 100644
--- a/overlays/default.nix
+++ b/overlays/default.nix
@@ -5,7 +5,8 @@ let
     (builtins.substring 4 2 longDate)
     (builtins.substring 6 2 longDate)
   ]);
-  mkVersionInput = input: "unstable" + mkDate (input.lastModifiedDate or "19700101") + "_" + (input.shortRev or "dirty");
+  mkVersionSrc = src: "unstable-" + builtins.substring 0 7 src.rev;
+  mkVersionInput = input: "unstable-" + mkDate (input.lastModifiedDate or "19700101") + "_" + (input.shortRev or "dirty");
 in
 {
   agenix = inputs.agenix.packages.${prev.system}.default;