diff --git a/conf/sip_profiles/internal.xml b/conf/sip_profiles/internal.xml
index c6d23c170b..9d56d1ec86 100644
--- a/conf/sip_profiles/internal.xml
+++ b/conf/sip_profiles/internal.xml
@@ -129,6 +129,8 @@
     <!-- add a ;received="<ip>:<port>" to the contact when replying to register for nat handling -->
     <!--<param name="NDLB-received-in-nat-reg-contact" value="true"/>-->
     <param name="auth-calls" value="$${internal_auth_calls}"/>
+    <!-- Force the user and auth-user to match. -->
+    <param name="inbound-reg-force-matching-username" value="true"/>
     <!-- on authed calls, authenticate *all* the packets not just invite -->
     <param name="auth-all-packets" value="false"/>
     <!-- <param name="ext-rtp-ip" value="$${external_rtp_ip}"/> -->