diff --git a/airtime_mvc/application/common/Billing.php b/airtime_mvc/application/common/Billing.php
index 6753f2326..8927cbc73 100644
--- a/airtime_mvc/application/common/Billing.php
+++ b/airtime_mvc/application/common/Billing.php
@@ -19,7 +19,10 @@ class Billing
         //XXX: Major hack attack. Since this function gets called often, rather than querying WHMCS
         //     we're just going to extract it from airtime.conf since it's the same as the rabbitmq username.
         $CC_CONFIG = Config::getConfig();
-        $instanceId = $CC_CONFIG['rabbitmq']['username'];
+        $instanceId = $CC_CONFIG['rabbitmq']['user'];
+        if (!is_numeric($instanceId)) {
+            throw new Exception("Invalid instance id in " . __FUNCTION__ . ": " . $instanceId);
+        }
         return $instanceId;
     }