diff --git a/conf/freeswitch.xml b/conf/freeswitch.xml
index df3076291c..6d1b836a98 100644
--- a/conf/freeswitch.xml
+++ b/conf/freeswitch.xml
@@ -78,7 +78,7 @@
         <!-- <param name="ip" value="1.2.3.4"> -->
         <param name="port" value="4569"/>
         <param name="dialplan" value="XML"/>
-        <param name="codec-prefs" value="PCMU,PCMA,speex,L16"/>
+        <param name="codec-prefs" value="PCMU@20,PCMA,speex,L16"/>
         <param name="codec-master" value="us"/>
         <param name="codec-rates" value="8"/>
       </settings>
@@ -116,7 +116,9 @@
         <param name="port" value="5060"/>
         <param name="dialplan" value="XML"/>
         <param name="dtmf-duration" value="100"/>
-        <param name="codec-prefs" value="PCMU,PCMA"/>
+        <!-- the @20 is optional number of ms you want to use.  Use it only
+        if you know the codec supports it -->
+        <param name="codec-prefs" value="PCMU@20,PCMA@20"/>
         <!-- Payload number to bind DTMF to-->
         <param name="rfc2833-pt" value="101"/>
         <!-- disable to trade async for more calls -->