diff --git a/zfs-backup.py b/zfs-backup.py
index 6469a78..1fe8d80 100755
--- a/zfs-backup.py
+++ b/zfs-backup.py
@@ -316,7 +316,7 @@ class Disk:
         if not self._decrypted:
             raise ValueError(NOT_DECRYPTED, self._name)
         # TODO use run instead?
-        get_output_of_command([config.CRYPTSETUP, "close", self._name])
+        get_output_of_command([config.CRYPTSETUP, "close", self._mapper_entry])
         self._decrypted = False