diff --git a/doc/manual/expressions/advanced-attributes.xml b/doc/manual/expressions/advanced-attributes.xml
index db981b607..a9b97b91a 100644
--- a/doc/manual/expressions/advanced-attributes.xml
+++ b/doc/manual/expressions/advanced-attributes.xml
@@ -322,6 +322,20 @@ big = "a very long string";
 
   </varlistentry>
 
+
+  <varlistentry><term><varname>allowSubstitutes</varname></term>
+
+    <listitem><para>If this attribute is set to
+    <literal>false</literal>, then Nix will always build this
+    derivation; it will not try to substitute its outputs. This is
+    useful for very trivial derivations (such as
+    <function>writeText</function> in Nixpkgs) that are cheaper to
+    build locally than to substitute from a binary
+    cache.</para></listitem>
+
+  </varlistentry>
+
+
 </variablelist>
 
 </section>