diff --git a/flake.nix b/flake.nix
index bafc820..8350516 100644
--- a/flake.nix
+++ b/flake.nix
@@ -18,7 +18,7 @@
           cargoLock = { lockFile = ./Cargo.lock; };
 
           NIX_SEMVER = version;
-          NIX_GIT_SHA_SHORT = if self ? rev then self.rev else "dirty";
+          NIX_GIT_SHA_SHORT = if self ? rev then builtins.substring 0 7 self.rev else "dirty";
         };
         packages.default = packages.fox32asm;
       }