diff --git a/nixos/doc/manual/development.xml b/nixos/doc/manual/development.xml
index b7b232fa8ef..13568868802 100644
--- a/nixos/doc/manual/development.xml
+++ b/nixos/doc/manual/development.xml
@@ -42,7 +42,7 @@ need to tell <command>nixos-rebuild</command> about them using the
 <option>-I</option> flag:
 
 <screen>
-$ nixos-rebuild switch -I <replaceable>/my/sources</replaceable>/nixpkgs
+$ nixos-rebuild switch -I nixpkgs=<replaceable>/my/sources</replaceable>/nixpkgs
 </screen>
 
 </para>