diff --git a/reference/session/functions/session-regenerate-id.xml b/reference/session/functions/session-regenerate-id.xml
index 0b9f117c12..1651e1171c 100644
--- a/reference/session/functions/session-regenerate-id.xml
+++ b/reference/session/functions/session-regenerate-id.xml
@@ -18,6 +18,11 @@
    <function>session_regenerate_id</function> will replace the current
    session id with a new one, and keep the current session information.
   </para>
+  <para>
+   When <link linkend="ini.session.use-trans-sid">session.use_trans_sid</link>
+   is enabled, output must be started after <function>session_regenerate_id</function>
+   call. Otherwise, old session ID is used.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">