diff --git a/homeassistant/components/slack/notify.py b/homeassistant/components/slack/notify.py index deba0796750..aae2846503d 100644 --- a/homeassistant/components/slack/notify.py +++ b/homeassistant/components/slack/notify.py @@ -166,7 +166,7 @@ class SlackNotificationService(BaseNotificationService): filename=filename, initial_comment=message, title=title or filename, - thread_ts=thread_ts, + thread_ts=thread_ts or "", ) except (SlackApiError, ClientError) as err: _LOGGER.error("Error while uploading file-based message: %r", err)