diff --git a/examples/dockwidgets/main.cpp b/examples/dockwidgets/main.cpp
index be3f94d3..3558fef6 100644
--- a/examples/dockwidgets/main.cpp
+++ b/examples/dockwidgets/main.cpp
@@ -82,16 +82,18 @@ int main(int argc, char **argv)
     QCommandLineOption maximizeButton("b", QCoreApplication::translate("main", "DockWidgets have maximize/restore buttons instead of float/dock button"));
     parser.addOption(maximizeButton);
 
-    QCommandLineOption dockableMainWindows("j", QCoreApplication::translate("main", "Allow main windows to be docked inside other main windows (this feature is work in progress)"));
+#ifdef KDDOCKWIDGETS_SUPPORTS_NESTED_MAINWINDOWS
+    QCommandLineOption dockableMainWindows("j", QCoreApplication::translate("main", "Allow main windows to be docked inside other main windows"));
+    parser.addOption(dockableMainWindows);
+#endif
+
     QCommandLineOption maxSizeOption("g", QCoreApplication::translate("main", "Make dock #8 have a max-size of 200x200. (this feature is work in progress)"));
     QCommandLineOption centralFrame("f", QCoreApplication::translate("main", "Persistent central frame"));
 
 #if defined(DOCKS_DEVELOPER_MODE)
     parser.addOption(centralFrame);
-    parser.addOption(dockableMainWindows);
     parser.addOption(maxSizeOption);
 #else
-    Q_UNUSED(dockableMainWindows)
     Q_UNUSED(maxSizeOption)
     Q_UNUSED(centralFrame)
 #endif
@@ -142,9 +144,14 @@ int main(int argc, char **argv)
     const bool restoreIsRelative = parser.isSet(relativeRestore);
     const bool nonDockableDockWidget9 = parser.isSet(nonDockable);
     const bool maxSizeForDockWidget8 = parser.isSet(maxSizeOption);
-    const bool usesDockableMainWindows = parser.isSet(dockableMainWindows);
     const bool usesMainWindowsWithAffinity = parser.isSet(multipleMainWindows);
 
+#ifdef KDDOCKWIDGETS_SUPPORTS_NESTED_MAINWINDOWS
+    const bool usesDockableMainWindows = parser.isSet(dockableMainWindows);
+#else
+    const bool usesDockableMainWindows = false;
+#endif
+
     MyMainWindow mainWindow(QStringLiteral("MyMainWindow"), options, nonClosableDockWidget0,
                             nonDockableDockWidget9, restoreIsRelative, maxSizeForDockWidget8);
     mainWindow.setWindowTitle("Main Window 1");
@@ -172,12 +179,22 @@ int main(int argc, char **argv)
 
         mainWindow2->resize(1200, 1200);
         mainWindow2->show();
-    } else if (parser.isSet(dockableMainWindows)) {
+    } else if (usesDockableMainWindows) {
+        auto mainWindowDockWidget = new DockWidget(QStringLiteral("MyMainWindow-2-DW"));
 
+        const QString affinity = QStringLiteral("Inner-DockWidgets-2");
         auto dockableMainWindow = new MyMainWindow(QStringLiteral("MyMainWindow-2"), options,
-                                                   false, false, restoreIsRelative, false);
+                                                   false, false, restoreIsRelative, false, affinity);
+
+        dockableMainWindow->setAffinities({ affinity });
+
+        dockableMainWindow->setStyleSheet(QStringLiteral("background: yellow"));
+
         dockableMainWindow->setWindowTitle("Dockable Main Window");
         dockableMainWindow->show();
+        mainWindowDockWidget->setWidget(dockableMainWindow);
+        mainWindowDockWidget->show();
+        mainWindowDockWidget->resize(800, 800);
     }
 
     return app.exec();
diff --git a/src/KDDockWidgets.h b/src/KDDockWidgets.h
index 3143143e..30f87af2 100644
--- a/src/KDDockWidgets.h
+++ b/src/KDDockWidgets.h
@@ -30,6 +30,13 @@
 
 #include <QObject>
 
+#ifdef Q_OS_WIN
+// Only on Windows, where this is popular. On linux it the Qt::Tool windows need reparenting. Untested on macOS.
+# define KDDOCKWIDGETS_SUPPORTS_NESTED_MAINWINDOWS
+#endif
+
+
+
 namespace KDDockWidgets
 {
     enum Location {
diff --git a/tests/tst_docks.cpp b/tests/tst_docks.cpp
index 915675ad..a2b4a656 100644
--- a/tests/tst_docks.cpp
+++ b/tests/tst_docks.cpp
@@ -51,6 +51,7 @@
 #include <QTextEdit>
 #include <QVBoxLayout>
 #include <QToolButton>
+#include <QMenuBar>
 #include <QStyleFactory>
 
 #ifdef Q_OS_WIN
@@ -5133,16 +5134,64 @@ void TestDocks::tst_dockableMainWindows()
      m1->addDockWidget(dock1, Location_OnTop);
 
      auto m2 = new KDDockWidgets::MainWindow("mainwindow-dockable");
-     auto dock2 = createDockWidget("mainwindow-dw", m2);
-     dock2->show();
+     auto m2Container = createDockWidget("mainwindow-dw", m2);
+     auto menubar = m2->menuBar();
+     menubar->addMenu("File");
+     menubar->addMenu("View");
+     menubar->addMenu("Help");
+     m2Container->show();
 
-     auto fw = qobject_cast<FloatingWindow*>(dock2->window());
-     TitleBar *titleBar = fw->titleBar();
+     auto dock21 = createDockWidget("dock21", new QPushButton("foo"));
+     auto dock22 = createDockWidget("dock22", new QPushButton("foo"));
+     m2->addDockWidget(dock21, Location_OnLeft);
+     m2->addDockWidget(dock22, Location_OnRight);
+
+     auto fw = qobject_cast<FloatingWindow*>(m2Container->window());
+     TitleBar *fwTitleBar = fw->titleBar();
+
+     QVERIFY(fw->hasSingleFrame());
+     QVERIFY(fw->hasSingleDockWidget());
+
+     // Check that the inner-inner dock widgets have a visible title-bar
+     QVERIFY(dock21->titleBar()->isVisible());
+     QVERIFY(dock22->titleBar()->isVisible());
+     QVERIFY(dock21->titleBar() != fwTitleBar);
+     QVERIFY(dock22->titleBar() != fwTitleBar);
 
      QTest::qWait(10); // the DND state machine needs the event loop to start, otherwise activeState() is nullptr. (for offscreen QPA)
-     const QPoint startPoint = titleBar->mapToGlobal(QPoint(5, 5));
+     const QPoint startPoint = fwTitleBar->mapToGlobal(QPoint(5, 5));
      const QPoint destination = startPoint + QPoint(20, 20);
-     drag(titleBar, startPoint, destination);
+
+     // Check that we don't get the "Refusing to itself" warning. not actually dropping anywhere
+     drag(fwTitleBar, startPoint, destination);
+
+     // The FloatingWindow has a single DockWidget, so it shows the title bar, while the Frame doesn't
+     QVERIFY(fwTitleBar->isVisible());
+     QVERIFY(!m2Container->frame()->titleBar()->isVisible());
+
+     fw->dropArea()->addDockWidget(dock1, Location::Location_OnLeft, nullptr);
+     // Now the FloatingWindow has two dock widgets, so our main window dock widget also shows the title bar
+     QVERIFY(fwTitleBar->isVisible());
+     QVERIFY(m2Container->frame()->titleBar()->isVisible());
+
+     // Put it how it was, FloatingWindow is single dock again
+     auto frame1 = dock1->frame();
+     dock1->close();
+     Testing::waitForDeleted(frame1);
+     QVERIFY(fwTitleBar->isVisible());
+     QVERIFY(!m2Container->frame()->titleBar()->isVisible());
+
+     // Repeat, but instead of closing dock1, we float it
+     fw->dropArea()->addDockWidget(dock1, Location::Location_OnLeft, nullptr);
+     QVERIFY(fwTitleBar->isVisible());
+     QVERIFY(m2Container->frame()->titleBar()->isVisible());
+     frame1 = dock1->frame();
+     frame1->titleBar()->onFloatClicked();
+     QVERIFY(fwTitleBar->isVisible());
+
+     QVERIFY(!m2Container->frame()->titleBar()->isVisible());
+
+     fw->dropArea()->addDockWidget(dock1, Location::Location_OnLeft, nullptr);
 }
 
 void TestDocks::tst_lastFloatingPositionIsRestored()