diff --git a/browser/components/sessionstore/src/nsSessionStartup.js b/browser/components/sessionstore/src/nsSessionStartup.js
index cbdc4cb0e13e..afe924288cc8 100644
--- a/browser/components/sessionstore/src/nsSessionStartup.js
+++ b/browser/components/sessionstore/src/nsSessionStartup.js
@@ -81,6 +81,8 @@ SessionStartup.prototype = {
    * Initialize the component
    */
   init: function sss_init() {
+    Services.obs.notifyObservers(null, "sessionstore-init-started", null);
+
     // do not need to initialize anything in auto-started private browsing sessions
     if (PrivateBrowsingUtils.permanentPrivateBrowsing) {
       this._initialized = true;
diff --git a/browser/components/sessionstore/test/browser_telemetry.js b/browser/components/sessionstore/test/browser_telemetry.js
index 7029c038e3cf..680e7c676ae4 100644
--- a/browser/components/sessionstore/test/browser_telemetry.js
+++ b/browser/components/sessionstore/test/browser_telemetry.js
@@ -242,6 +242,15 @@ add_task(function formdata() {
   }
 });
 
+add_task(function* test_sessionRestoreInit() {
+   let info = Cc["@mozilla.org/toolkit/app-startup;1"].
+     getService(Ci.nsIAppStartup).
+     getStartupInfo();
+  ok(info.sessionRestoreInit > info.process, "sessionRestoreInit is after process creation");
+  ok(info.sessionRestoreInit <
+    Date.now() + 10000 /* Date.now() is non-monotonic, let's play it paranoid*/,
+    "sessionRestoreInit is before now");
+});
 
 /**
  * Get the latest statistics.
diff --git a/toolkit/components/startup/StartupTimeline.h b/toolkit/components/startup/StartupTimeline.h
index f035dc0042a5..74aa7775a4ea 100644
--- a/toolkit/components/startup/StartupTimeline.h
+++ b/toolkit/components/startup/StartupTimeline.h
@@ -13,6 +13,7 @@ mozilla_StartupTimeline_Event(AFTER_PROFILE_LOCKED, "afterProfileLocked")
 mozilla_StartupTimeline_Event(STARTUP_CRASH_DETECTION_BEGIN, "startupCrashDetectionBegin")
 mozilla_StartupTimeline_Event(STARTUP_CRASH_DETECTION_END, "startupCrashDetectionEnd")
 mozilla_StartupTimeline_Event(FIRST_PAINT, "firstPaint")
+mozilla_StartupTimeline_Event(SESSION_RESTORE_INIT, "sessionRestoreInit")
 mozilla_StartupTimeline_Event(SESSION_RESTORED, "sessionRestored")
 mozilla_StartupTimeline_Event(CREATE_TOP_LEVEL_WINDOW, "createTopLevelWindow")
 mozilla_StartupTimeline_Event(LINKER_INITIALIZED, "linkerInitialized")
diff --git a/toolkit/components/startup/nsAppStartup.cpp b/toolkit/components/startup/nsAppStartup.cpp
index a0bab7fb93a9..9e9ecb7bca01 100644
--- a/toolkit/components/startup/nsAppStartup.cpp
+++ b/toolkit/components/startup/nsAppStartup.cpp
@@ -161,6 +161,7 @@ nsAppStartup::Init()
     return NS_ERROR_FAILURE;
 
   os->AddObserver(this, "quit-application-forced", true);
+  os->AddObserver(this, "sessionstore-init-started", true);
   os->AddObserver(this, "sessionstore-windows-restored", true);
   os->AddObserver(this, "profile-change-teardown", true);
   os->AddObserver(this, "xul-window-registered", true);
@@ -705,6 +706,8 @@ nsAppStartup::Observe(nsISupports *aSubject,
       mPlacesInitCompleteProbe->Trigger();
     }
 #endif //defined(XP_WIN)
+  } else if (!strcmp(aTopic, "sessionstore-init-started")) {
+    StartupTimeline::Record(StartupTimeline::SESSION_RESTORE_INIT);
   } else if (!strcmp(aTopic, "xpcom-shutdown")) {
     Telemetry::EnteringShutdownStage();
 #if defined(XP_WIN)