diff --git a/app/fax_queue/resources/job/fax_send.php b/app/fax_queue/resources/job/fax_send.php
index f0c1fa556a..4f295f545f 100644
--- a/app/fax_queue/resources/job/fax_send.php
+++ b/app/fax_queue/resources/job/fax_send.php
@@ -394,7 +394,7 @@
 			//$dial_string .= "fax_retry_sleep=180,";
 			$dial_string .= "fax_verbose=true,";
 			//$dial_string .= "fax_use_ecm=off,";
-			$dial_string .= "absolute_codec_string=PCMU,PCMA,";
+			$dial_string .= "absolute_codec_string=\'PCMU,PCMA\',";
 			$dial_string .= "api_hangup_hook='lua app/fax/resources/scripts/hangup_tx.lua'";
 
 		//connect to event socket and send the command