diff --git a/disk_password_gui/disk_password_gui.py b/disk_password_gui/disk_password_gui.py
index f1d2098..1312202 100644
--- a/disk_password_gui/disk_password_gui.py
+++ b/disk_password_gui/disk_password_gui.py
@@ -289,6 +289,7 @@ def _do_reencrypt(self):
             except Exception as ex:  # pylint: disable=broad-except
                 self.errors.append(str(ex))
 
+        assert self.busy_dialog is not None
         self.busy_dialog.hide()
         GLib.idle_add(self._busy_ended)