diff --git a/release.nix b/release.nix
index c93e2d1..7dca756 100644
--- a/release.nix
+++ b/release.nix
@@ -7,8 +7,8 @@ let
   pkgs = import nixpkgs { system = "x86_64-linux"; };
   version = "1.7" +
             (if officialRelease then ""
-             else if src ? lastModified then "${builtins.substring 0 8 src.lastModified}.${src.shortRev}"
-             else "${toString src.revCount}_${src.shortRev}");
+             else if src ? lastModified then "pre${builtins.substring 0 8 src.lastModified}.${src.shortRev}"
+             else "pre${toString src.revCount}_${src.shortRev}");
 in
 
 rec {