diff --git a/doc/manual/installation.xml b/doc/manual/installation.xml
index bed96cd885..9e73fb69a2 100644
--- a/doc/manual/installation.xml
+++ b/doc/manual/installation.xml
@@ -314,7 +314,7 @@ bit turned on (like <filename>/tmp</filename>):
 
 <screen>
 $ chgrp nixbld /nix/store
-$ chmod 1777 /nix/store
+$ chmod 1775 /nix/store
 </screen>
 
 </para>