diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index f44c6aa9052..c2ca5bda610 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -5093,6 +5093,10 @@ var TabsInTitlebar = {
 #endif
   },
 
+  get enabled() {
+    return document.documentElement.getAttribute("tabsintitlebar") == "true";
+  },
+
 #ifdef CAN_DRAW_IN_TITLEBAR
   observe: function (subject, topic, data) {
     if (topic == "nsPref:changed")
@@ -5118,8 +5122,7 @@ var TabsInTitlebar = {
       break;
     }
 
-    let docElement = document.documentElement;
-    if (allowed == (docElement.getAttribute("tabsintitlebar") == "true"))
+    if (allowed == this.enabled)
       return;
 
     function $(id) document.getElementById(id);
@@ -5140,20 +5143,18 @@ var TabsInTitlebar = {
       titlebar.style.marginBottom = - Math.min(tabsToolbarRect.top - titlebarTop,
                                                tabsToolbarRect.height) + "px";
 
-      docElement.setAttribute("tabsintitlebar", "true");
+      document.documentElement.setAttribute("tabsintitlebar", "true");
 
       if (!this._draghandle) {
         let tmp = {};
         Components.utils.import("resource://gre/modules/WindowDraggingUtils.jsm", tmp);
         this._draghandle = new tmp.WindowDraggingElement(tabsToolbar, window);
         this._draghandle.mouseDownCheck = function () {
-          return !this._dragBindingAlive &&
-                 this.ownerDocument.documentElement
-                     .getAttribute("tabsintitlebar") == "true";
+          return !this._dragBindingAlive && TabsInTitlebar.enabled;
         };
       }
     } else {
-      docElement.removeAttribute("tabsintitlebar");
+      document.documentElement.removeAttribute("tabsintitlebar");
 
       titlebar.style.marginBottom = "";
     }
diff --git a/browser/base/content/tabbrowser.xml b/browser/base/content/tabbrowser.xml
index d192b764c6a..abeefc7476f 100644
--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -3203,19 +3203,24 @@
       ]]></handler>
 
       <handler event="dblclick"><![CDATA[
-#ifdef MOZ_WIDGET_GTK2
-        // Disable this on GTK2 when the menubar is draggable, since (a)
-        // the menubar and tabbbar have unified appearance and should
-        // thus not have different behavior (though this condition alone
-        // applies to more cases) and (b) it interacts badly with the
-        // drag handling that we use for dragging either one.
-        if (this.parentNode._dragBindingAlive)
+#ifndef XP_MACOSX
+        // When the tabbar has an unified appearance with the titlebar
+        // and menubar, a double-click in it should have the same behavior
+        // as double-clicking the titlebar
+        if (TabsInTitlebar.enabled ||
+            (TabsOnTop.enabled && this.parentNode._dragBindingAlive))
           return;
 #endif
+
+        if (event.button != 0 ||
+            event.originalTarget.localName != "box")
+          return;
+
         // See hack note in the tabbrowser-close-tab-button binding
-        if (!this._blockDblClick && event.button == 0 &&
-            event.originalTarget.localName == "box")
+        if (!this._blockDblClick)
           BrowserOpenTab();
+
+        event.preventDefault();
       ]]></handler>
 
       <handler event="click"><![CDATA[
diff --git a/widget/src/windows/nsWindow.cpp b/widget/src/windows/nsWindow.cpp
index 8a1d89a49b2..744f2eeda8e 100644
--- a/widget/src/windows/nsWindow.cpp
+++ b/widget/src/windows/nsWindow.cpp
@@ -5072,6 +5072,17 @@ PRBool nsWindow::ProcessMessage(UINT msg, WPARAM &wParam, LPARAM &lParam,
       }
       break;
 
+    case WM_NCLBUTTONDBLCLK:
+      DispatchMouseEvent(NS_MOUSE_DOUBLECLICK, 0, lParamToClient(lParam),
+                         PR_FALSE, nsMouseEvent::eLeftButton,
+                         MOUSE_INPUT_SOURCE());
+      result = 
+        DispatchMouseEvent(NS_MOUSE_BUTTON_UP, 0, lParamToClient(lParam),
+                           PR_FALSE, nsMouseEvent::eLeftButton,
+                           MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
     case WM_APPCOMMAND:
     {
       PRUint32 appCommand = GET_APPCOMMAND_LPARAM(lParam);