diff --git a/modules/nixos/frajul-auto-upgrade.nix b/modules/nixos/frajul-auto-upgrade.nix
index 89456f2..2a55261 100644
--- a/modules/nixos/frajul-auto-upgrade.nix
+++ b/modules/nixos/frajul-auto-upgrade.nix
@@ -64,6 +64,9 @@ in {
           exit 1
         fi
 
+        echo $$ > "$LOCK_FILE"
+        trap 'rm -f "$LOCK_FILE"' EXIT
+
         if /run/current-system/sw/bin/nix flake update --flake "${cfg.flakePath}" && /run/current-system/sw/bin/nixos-rebuild switch --flake "${cfg.flakePath}"; then
             echo "success" > "$LAST_STATUS_FILE"
         else