diff --git a/zfs-backup.py b/zfs-backup.py
index 1df4d7c..69a889d 100755
--- a/zfs-backup.py
+++ b/zfs-backup.py
@@ -447,8 +447,9 @@ class Dataset:
         for snapshot in old_snapshots:
             snapshot.destroy()
 
+    @staticmethod
     def _get_n_oldest_snapshots(
-        self, snapshots: list[Snapshot], count: int
+            snapshots: list[Snapshot], count: int
     ) -> list[Snapshot]:
         snapshots.sort()
         return snapshots[:count]