--- a/browser/modules/BrowserUsageTelemetry.jsm
+++ b/browser/modules/BrowserUsageTelemetry.jsm
@@ -13,16 +13,18 @@ this.EXPORTED_SYMBOLS = [
 
 const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
 
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
 XPCOMUtils.defineLazyModuleGetter(this, "PrivateBrowsingUtils",
                                   "resource://gre/modules/PrivateBrowsingUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "SessionStore",
+                                  "resource:///modules/sessionstore/SessionStore.jsm");
 
 // The upper bound for the count of the visited unique domain names.
 const MAX_UNIQUE_VISITED_DOMAINS = 100;
 
 // Observed topic names.
 const WINDOWS_RESTORED_TOPIC = "sessionstore-windows-restored";
 const TAB_RESTORING_TOPIC = "SSTabRestoring";
 const TELEMETRY_SUBSESSIONSPLIT_TOPIC = "internal-telemetry-after-subsession-split";
@@ -94,16 +96,22 @@ function getOpenTabsAndWinsCounts() {
     let win = browserEnum.getNext();
     winCount++;
     tabCount += win.gBrowser.tabs.length;
   }
 
   return { tabCount, winCount };
 }
 
+function getTabCount() {
+  let {windows} = SessionStore.getCurrentState();
+  return windows.map(win => win.isPrivate ? 0 : win.tabs.length)
+                .reduce((tabcount, accumulator) => tabcount + accumulator, 0);
+}
+
 function getSearchEngineId(engine) {
   if (engine) {
     if (engine.identifier) {
       return engine.identifier;
     }
     // Due to bug 1222070, we can't directly check Services.telemetry.canRecordExtended
     // here.
     const extendedTelemetry = Services.prefs.getBoolPref("toolkit.telemetry.enabled");