--- a/mod_bookmarks2/README.markdown	Tue Dec 01 16:45:20 2020 +0100
+++ b/mod_bookmarks2/README.markdown	Thu Dec 03 19:25:33 2020 +0100
@@ -4,6 +4,17 @@
 summary: Synchronise bookmarks between Private XML and PEP
 ...
 
+::: {.alert .alert-warning}
+**WARNING:** This module is incompatible with clients which only use
+[deprecated PEP bookmarks
+(XEP-0048)](https://xmpp.org/extensions/xep-0048.html), such as
+[Converse.js](https://conversejs.org).
+
+If you need to be compatible with these clients, use
+[mod\_bookmarks](mod_bookmarks.html) instead.
+:::
+
+
 Introduction
 ------------