diff --git a/nixos/doc/manual/configuration/declarative-packages.xml b/nixos/doc/manual/configuration/declarative-packages.xml
index be9884fe9dc..c9acbefea60 100644
--- a/nixos/doc/manual/configuration/declarative-packages.xml
+++ b/nixos/doc/manual/configuration/declarative-packages.xml
@@ -27,8 +27,13 @@ nixos.firefox   firefox-23.0   Mozilla Firefox - the browser, reloaded
 <replaceable>...</replaceable>
 </screen>
   The first column in the output is the <emphasis>attribute name</emphasis>,
-  such as <literal>nixos.thunderbird</literal>. (The <literal>nixos</literal>
-  prefix allows distinguishing between different channels that you might have.)
+  such as <literal>nixos.thunderbird</literal>.
+ </para>
+ <para>
+  Note: the <literal>nixos</literal> prefix tells us that we want to get the
+  package from the <literal>nixos</literal> channel and works only in CLI tools.
+
+  In declarative configuration use <literal>pkgs</literal> prefix (variable).
  </para>
 
  <para>