--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -8438,16 +8438,31 @@ var RestoreLastSessionObserver = {
         gBrowser.tabContainer.updateSessionRestoreVisibility();
         restoreTabsButton.style.maxWidth = `${restoreTabsButtonWrapperWidth}px`;
         gBrowser.tabContainer.addEventListener("TabOpen", this);
         Services.telemetry.scalarSet("browser.session.restore.tabbar_restore_available", true);
         restoreTabsButton.addEventListener("click", () => {
           Services.telemetry.scalarSet("browser.session.restore.tabbar_restore_clicked", true);
         });
       }
+      let { windows, tabs } = SessionStore.restorableObjectsCount;
+      let winsBase = gNavigatorBundle.getString("menuRestoreLastSessionWindowCount");
+      let tabsBase = gNavigatorBundle.getString("menuRestoreLastSessionTabsCount");
+      let ending;
+      if (windows > 1) {
+        let labelVars = [PluralForm.get(windows, winsBase).replace("#1", windows),
+                         PluralForm.get(tabs, tabsBase).replace("#1", tabs)];
+        ending = gNavigatorBundle.getFormattedString("menuRestoreLastSessionCount",
+                                                     labelVars);
+      } else {
+        ending = PluralForm.get(tabs, tabsBase).replace("#1", tabs);
+      }
+      let label = gNavigatorBundle.getFormattedString("menuRestoreLastSessionLabel", [ending]);
+      document.getElementById("Browser:RestoreLastSession").setAttribute("label", label);
+
       Services.obs.addObserver(this, "sessionstore-last-session-cleared", true);
       goSetCommandEnabled("Browser:RestoreLastSession", true);
     } else if (SessionStartup.isAutomaticRestoreEnabled()) {
       document.getElementById("Browser:RestoreLastSession").setAttribute("hidden", true);
     }
   },
 
   handleEvent(event) {
@@ -8471,16 +8486,20 @@ var RestoreLastSessionObserver = {
     restoreTabsButton.style.maxWidth = 0;
     gBrowser.tabContainer.removeEventListener("TabOpen", this);
   },
 
   observe() {
     // The last session can only be restored once so there's
     // no way we need to re-enable our menu item.
     Services.obs.removeObserver(this, "sessionstore-last-session-cleared");
+    document.getElementById("Browser:RestoreLastSession").setAttribute(
+      "label",
+      gNavigatorBundle.getFormattedString("menuRestoreLastSessionLabel", [""])
+    );
     goSetCommandEnabled("Browser:RestoreLastSession", false);
     this.removeRestoreButton();
   },
 
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver,
                                          Ci.nsISupportsWeakReference])
 };
 

--- a/browser/locales/en-US/chrome/browser/browser.properties
+++ b/browser/locales/en-US/chrome/browser/browser.properties
@@ -423,16 +423,29 @@ menuRestoreAllWindows.label=Restore All 
 # LOCALIZATION NOTE (menuRestoreAllWindowsSubview.label): like menuRestoreAllWindows.label,
 # but used in the history subview in the panel UI, so needs to mention these are *closed* windows.
 menuRestoreAllWindowsSubview.label=Restore Closed Windows
 # LOCALIZATION NOTE (menuUndoCloseWindowLabel): Semicolon-separated list of plural forms.
 # See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
 # #1 Window Title, #2 Number of tabs
 menuUndoCloseWindowLabel=#1 (and #2 other tab);#1 (and #2 other tabs)
 menuUndoCloseWindowSingleTabLabel=#1
+# LOCALIZATION NOTE (menuRestoreLastSessionLabel): Replaces historyRestoreLastSession.label
+# from browser.dtd with counts
+# %S is menuRestoreLastSessionCount, or menuRestoreLastSessionTabsCount if 1 window
+menuRestoreLastSessionLabel=Restore Previous Session %S
+# LOCALIZATION NOTE (menuRestoreLastSessionCount): %1$S is
+# menuRestoreLastSessionWindowCount, %2$S is menuRestoreLastSessionTabCount
+menuRestoreLastSessionCount=%1$S / %2$S
+# LOCALIZATION NOTE (menuRestoreLastSessionWindowsCount): Semicolon-separated list of plural forms.
+# See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
+menuRestoreLastSessionWindowCount=#1 window;#1 windows
+# LOCALIZATION NOTE (menuRestoreLastSessionTabsCount): Semicolon-separated list of plural forms.
+# See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
+menuRestoreLastSessionTabsCount=#1 tab;#1 tabs
 
 # Unified Back-/Forward Popup
 tabHistory.current=Stay on this page
 tabHistory.goBack=Go back to this page
 tabHistory.goForward=Go forward to this page
 
 # URL Bar
 pasteAndGo.label=Paste & Go