diff --git a/zfs-backup.py b/zfs-backup.py
index d4dc4f9..f6b7b97 100755
--- a/zfs-backup.py
+++ b/zfs-backup.py
@@ -272,6 +272,7 @@ class ZFS:
         # -u  File system that is associated with the received stream is not mounted.
         if not isinstance(pool, Pool):
             raise TypeError("Can only receive into pools.")
+        # TODO use internal functions
         check_output(
             [config.ZFS, "receive", "-d", "-F", "-u", pool.name],
             stdin=stream.stdout,