2 files changed, 13 insertions, 3 deletions
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index fa26fd77a3..f061a2bf50 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -402,7 +402,7 @@ void QWindowPrivate::create(bool recursive)
         q->parent()->create();
 
     platformWindow = QGuiApplicationPrivate::platformIntegration()->createPlatformWindow(q);
-    Q_ASSERT(platformWindow);
+    Q_ASSERT(platformWindow || q->type() == Qt::ForeignWindow);
 
     if (!platformWindow) {
         qWarning() << "Failed to create platform window for" << q << "with flags" << q->flags();
@@ -2432,7 +2432,8 @@ QWindow *QWindowPrivate::topLevelWindow() const
     This can be used, on platforms which support it, to embed a QWindow inside a
     native window, or to embed a native window inside a QWindow.
 
-    If foreign windows are not supported, this function returns 0.
+    If foreign windows are not supported or embedding the native window
+    failed in the platform plugin, this function returns 0.
 
     \note The resulting QWindow should not be used to manipulate the underlying
     native window (besides re-parenting), or to observe state changes of the
@@ -2453,6 +2454,10 @@ QWindow *QWindow::fromWinId(WId id)
     window->setFlags(Qt::ForeignWindow);
     window->setProperty("_q_foreignWinId", QVariant::fromValue(id));
     window->create();
+    if (!window->handle()) {
+        delete window;
+        return nullptr;
+    }
     return window;
 }
 
diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index 6142aac92e..debe6dd131 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -311,7 +311,12 @@ QPlatformWindow *QWindowsIntegration::createPlatformWindow(QWindow *window) cons
     }
 
     if (window->type() == Qt::ForeignWindow) {
-        QWindowsForeignWindow *result = new QWindowsForeignWindow(window, reinterpret_cast<HWND>(window->winId()));
+        const HWND hwnd = reinterpret_cast<HWND>(window->winId());
+        if (!IsWindow(hwnd)) {
+           qWarning("Windows QPA: Invalid foreign window ID %p.");
+           return nullptr;
+        }
+        QWindowsForeignWindow *result = new QWindowsForeignWindow(window, hwnd);
         const QRect obtainedGeometry = result->geometry();
         QScreen *screen = Q_NULLPTR;
         if (const QPlatformScreen *pScreen = result->screenForGeometry(obtainedGeometry))