diff --git a/final/configuration.nix b/final/configuration.nix
index 3248d68..0bfe35d 100644
--- a/final/configuration.nix
+++ b/final/configuration.nix
@@ -30,6 +30,13 @@
 
     delete_subvolume_recursively() {
         IFS=$'\n'
+
+        # If we accidentally end up with a file or directory under old_roots,
+        # the code will enumerate all subvolumes under the main volume.
+        # We don't want to remove everything under true main volume. Only
+        # proceed if this path is a btrfs subvolume (inode=256).
+        if [ $(stat -c %i "$1") -ne 256 ]; then return; fi
+
         for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
             delete_subvolume_recursively "/btrfs_tmp/$i"
         done