diff --git a/backup.nix b/backup.nix
index 94a376d..be2102e 100644
--- a/backup.nix
+++ b/backup.nix
@@ -7,6 +7,7 @@ let
       pkgs.restic
     ];
     text = ''
+      # shellcheck disable=SC2031
       if [ -z "$BACKUP_HELPER_DIRS"  ]; then
         echo "BACKUP_HELPER_DIRS is not set"
         exit 1;
@@ -18,7 +19,7 @@ let
         if [ $rc -ne 0 ]; then
           echo "Backup of $i failed with exit code $rc:"
           echo "$output"
-          exit_code=1;
+          exit_code="$rc";
         else
           echo "Backup of $i successful:"
           echo "$output"