diff --git a/backup.nix b/backup.nix
index 9909f46..3c6d5bb 100644
--- a/backup.nix
+++ b/backup.nix
@@ -15,7 +15,7 @@ let
       for i in ''${BACKUP_HELPER_DIRS//,/ }; do
         echo "Starting backup of $i";
         if ! output=$(restic backup "$i"); then
-          exit_code="$?";
+          exit_code=1;
           echo "Backup of $i failed with exit code $?:"
           echo "$output"
         else