diff --git a/nixos/doc/manual/release-notes/rl-1803.xml b/nixos/doc/manual/release-notes/rl-1803.xml
index 830e7cdd269..47522fe3cc9 100644
--- a/nixos/doc/manual/release-notes/rl-1803.xml
+++ b/nixos/doc/manual/release-notes/rl-1803.xml
@@ -71,6 +71,8 @@ following incompatible changes:</para>
 <itemizedlist>
   <listitem>
     <para>
+      ZNC option <option>services.znc.mutable</option> now defaults to <literal>true</literal>.
+      That means that old configuration is not overwritten by default when update to the znc options are made.
     </para>
   </listitem>
 </itemizedlist>