diff --git a/manpages/shorewall-providers.xml b/manpages/shorewall-providers.xml
index 4433f8568..39924f211 100644
--- a/manpages/shorewall-providers.xml
+++ b/manpages/shorewall-providers.xml
@@ -188,8 +188,11 @@
 
               <listitem>
                 <para>If the interface named in the INTERFACE column is not up
-                and configured with an IPv4 address then ignore this
-                provider.</para>
+                and configured with an IPv4 address then ignore this provider.
+                If not specified, the value of the <option>optional</option>
+                option for the INTERFACE in <ulink
+                url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)
+                is assumed.</para>
               </listitem>
             </varlistentry>