diff --git a/audio/2.0/config/audio_policy_configuration.xsd b/audio/2.0/config/audio_policy_configuration.xsd
index 8c05763..0a52b55 100644
--- a/audio/2.0/config/audio_policy_configuration.xsd
+++ b/audio/2.0/config/audio_policy_configuration.xsd
@@ -148,6 +148,11 @@
                     <xs:selector xpath="devicePorts/devicePort"/>
                     <xs:field xpath="@tagName"/>
                 </xs:key>
+                <xs:unique name="devicePortUniqueness">
+                    <xs:selector xpath="devicePorts/devicePort"/>
+                    <xs:field xpath="@type"/>
+                    <xs:field xpath="@address"/>
+                </xs:unique>
                 <xs:keyref name="defaultOutputDeviceRef" refer="devicePortNameKey">
                     <xs:selector xpath="defaultOutputDevice"/>
                     <xs:field xpath="."/>
@@ -419,7 +424,7 @@
                     <xs:attribute name="tagName" type="xs:token" use="required"/>
                     <xs:attribute name="type" type="audioDevice" use="required"/>
                     <xs:attribute name="role" type="role" use="required"/>
-                    <xs:attribute name="address" type="xs:string" use="optional"/>
+                    <xs:attribute name="address" type="xs:string" use="optional" default=""/>
                 </xs:complexType>
                 <xs:unique name="devicePortProfileUniqueness">
                     <xs:selector xpath="profile"/>