diff --git a/nixos/doc/manual/release-notes/rl-1903.xml b/nixos/doc/manual/release-notes/rl-1903.xml
index eca280afdf1..d00ffdbb04d 100644
--- a/nixos/doc/manual/release-notes/rl-1903.xml
+++ b/nixos/doc/manual/release-notes/rl-1903.xml
@@ -378,6 +378,15 @@
     (<link xlink:href="https://github.com/NixOS/nixpkgs/pull/54637">#54637</link>)
    </para>
   </listitem>
+  <listitem>
+   <para>
+    <literal>matrix-synapse</literal> has been updated to version 0.99. It will
+    <link xlink:href="https://github.com/matrix-org/synapse/pull/4509">no longer generate a self-signed certificate on first launch</link>
+    and will be <link xlink:href="https://matrix.org/blog/2019/02/05/synapse-0-99-0/">the last version to accept self-signed certificates</link>.
+    As such, it is now recommended to use a proper certificate verified by a
+    root CA (for example Let's Encrypt).
+   </para>
+  </listitem>
   </itemizedlist>
  </section>