--- a/mobile/android/chrome/content/Reader.js
+++ b/mobile/android/chrome/content/Reader.js
@@ -148,19 +148,19 @@ var Reader = {
       }
     }
   },
 
   pageAction: {
     readerModeCallback: function(browser) {
       let url = browser.currentURI.spec;
       if (url.startsWith("about:reader")) {
-        UITelemetry.addEvent("action.1", "button", "reader_exit");
+        UITelemetry.addEvent("action.1", "button", null, "reader_exit");
       } else {
-        UITelemetry.addEvent("action.1", "button", "reader_enter");
+        UITelemetry.addEvent("action.1", "button", null, "reader_enter");
       }
       browser.messageManager.sendAsyncMessage("Reader:ToggleReaderMode");
     },
   },
 
   updatePageAction: function(tab) {
     if (!tab.getActive()) {
       return;
@@ -189,19 +189,19 @@ var Reader = {
       return;
     }
 
     // Only stop a reader session if the foreground viewer is not visible.
     UITelemetry.stopSession("reader.1", "", null);
 
     if (browser.isArticle) {
       showPageAction("drawable://reader", Strings.reader.GetStringFromName("readerView.enter"));
-      UITelemetry.addEvent("show.1", "button", "reader_available");
+      UITelemetry.addEvent("show.1", "button", null, "reader_available");
     } else {
-      UITelemetry.addEvent("show.1", "button", "reader_unavailable");
+      UITelemetry.addEvent("show.1", "button", null, "reader_unavailable");
     }
   },
 
   /**
    * Gets an article for a given URL. This method will download and parse a document
    * if it does not find the article in the cache.
    *
    * @param url The article URL.