diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index f539d001280b..da01693263e2 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -3815,7 +3815,8 @@ Sub-options for this setting include:
 * `system_mxid_display_name`: set the display name of the "notices" user
 * `system_mxid_avatar_url`: set the avatar for the "notices" user
 * `room_name`: set the room name of the server notices room
-* `auto_join`: the user will be automatically joined to the room instead of being invited
+* `auto_join`: the user will be automatically joined to the room instead of being invited.
+  Defaults to false. _Added in Synapse 1.98.0._
 Example configuration:
 ```yaml
 server_notices: