diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index d01eb9a36..36964825e 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -1900,6 +1900,7 @@ var httpObserver = {
         16: 'websocket',
         17: 'csp_report',
         19: 'beacon',
+        20: 'xmlhttprequest',
         21: 'image'
     },
     onBeforeRequest: function(){},