1 files changed, 3 insertions, 0 deletions
diff --git a/docs/admin_api/purge_history_api.rst b/docs/admin_api/purge_history_api.rst
index f7be226fd9..f2c4dc03ac 100644
--- a/docs/admin_api/purge_history_api.rst
+++ b/docs/admin_api/purge_history_api.rst
@@ -8,6 +8,9 @@ Depending on the amount of history being purged a call to the API may take
 several minutes or longer. During this period users will not be able to
 paginate further back in the room from the point being purged from.
 
+Note that, in order to not break the room, this API won't delete the last
+message sent to it.
+
 The API is:
 
 ``POST /_synapse/admin/v1/purge_history/<room_id>[/<event_id>]``