diff --git a/doc/carddatabase_v4/cards.xsd b/doc/carddatabase_v4/cards.xsd
index 92d30b94f..6871cba4e 100644
--- a/doc/carddatabase_v4/cards.xsd
+++ b/doc/carddatabase_v4/cards.xsd
@@ -6,6 +6,7 @@
                 <xs:attribute type="xs:string" name="exclude" use="optional" />
                 <xs:attribute type="xs:string" name="attach" use="optional" />
                 <xs:attribute type="xs:string" name="persistent" use="optional" />
+                <xs:attribute type="xs:string" name="facedown" use="optional" />
             </xs:extension>
         </xs:simpleContent>
     </xs:complexType>