diff --git a/openjpa-project/src/doc/manual/ref_guide_mapping.xml b/openjpa-project/src/doc/manual/ref_guide_mapping.xml
index a998102..047ab01 100644
--- a/openjpa-project/src/doc/manual/ref_guide_mapping.xml
+++ b/openjpa-project/src/doc/manual/ref_guide_mapping.xml
@@ -1187,8 +1187,10 @@
                     <listitem>
                         <para>
 <literal>IndexPhysicalForeignKeys</literal>: Boolean property controlling
-whether to create explicit indexes on real physical foreign keys.
-The default value will be taken from the corresponding <literal>DBDictionary</literal> attribute.
+whether to create explicit indexes for real physical foreign keys depending on
+the corresponding <literal>DBDictionary</literal> attribute.
+Set this to <litreral>true</litreral> if you want to make sure that foreign keys are indexed.
+Defaults to false for backward compatibility reasons.
                         </para>
                     </listitem>
                     <listitem>