diff --git a/nixos/doc/manual/development/building-nixos.xml b/nixos/doc/manual/development/building-nixos.xml
index 150fa1d7017..2f963f8666f 100644
--- a/nixos/doc/manual/development/building-nixos.xml
+++ b/nixos/doc/manual/development/building-nixos.xml
@@ -12,12 +12,12 @@ your <filename>configuration.nix</filename> to configure the system that
 would be installed on the CD.</para>
 
 <para>Default CD/DVD configurations are available
-inside <filename>nixos/modules/installer/cd-dvd</filename>.  To build them
-you have to set <envar>NIXOS_CONFIG</envar> before
-running <command>nix-build</command> to build the ISO.
+inside <filename>nixos/modules/installer/cd-dvd</filename>.
 
 <screen>
-$ nix-build -A config.system.build.isoImage -I nixos-config=modules/installer/cd-dvd/installation-cd-minimal.nix</screen>
+$ git clone https://github.com/NixOS/nixpkgs.git
+$ cd nixpkgs/nixos
+$ nix-build -A config.system.build.isoImage -I nixos-config=modules/installer/cd-dvd/installation-cd-minimal.nix default.nix</screen>
 
 </para>