diff --git a/reference/intl/collator/sort.xml b/reference/intl/collator/sort.xml
index a89ec6dab8..4a9825f9f8 100644
--- a/reference/intl/collator/sort.xml
+++ b/reference/intl/collator/sort.xml
@@ -83,6 +83,7 @@
         </listitem>
        </itemizedlist>
        Default sorting type is <constant>Collator::SORT_REGULAR</constant>.
+       It is also used if an invalid $sort_flag value has been specified.
       </para>
      </listitem>
     </varlistentry>