diff --git a/doc/configuration.xml b/doc/configuration.xml
index 0d9786c2d6a2..6720f54374a1 100644
--- a/doc/configuration.xml
+++ b/doc/configuration.xml
@@ -272,7 +272,7 @@
      very short names:
 <programlisting>
 {
-  allowInsecurePredicate = (pkg: (builtins.stringLength (lib.getName pkg) &lt;= 5);
+  allowInsecurePredicate = pkg: builtins.stringLength (lib.getName pkg) &lt;= 5;
 }
 </programlisting>
     </para>