diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 93e838d8b82..361e12887a6 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -2201,7 +2201,7 @@ void QWidgetPrivate::updateIsTranslucent()
     if (QWindow *window = q->windowHandle()) {
         QSurfaceFormat format = window->format();
         const int oldAlpha = format.alphaBufferSize();
-        const int newAlpha = q->testAttribute(Qt::WA_TranslucentBackground)? 8 : 0;
+        const int newAlpha = q->testAttribute(Qt::WA_TranslucentBackground) ? 8 : -1;
         if (oldAlpha != newAlpha) {
             // QTBUG-85714: Do this only when the QWindow has not yet been create()'ed yet.
             //
diff --git a/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp b/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp
index f90879ab124..9d94aa5aca8 100644
--- a/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp
+++ b/tests/auto/widgets/widgets/qopenglwidget/tst_qopenglwidget.cpp
@@ -47,6 +47,8 @@ private slots:
     void offscreen();
     void offscreenThenOnscreen();
     void paintWhileHidden();
+    void widgetWindowColorFormat_data();
+    void widgetWindowColorFormat();
 
 #ifdef QT_BUILD_INTERNAL
     void staticTextDanglingPointer();
@@ -793,6 +795,30 @@ void tst_QOpenGLWidget::paintWhileHidden()
     QTRY_VERIFY(w->m_paintCalled > 0);
 }
 
+void tst_QOpenGLWidget::widgetWindowColorFormat_data()
+{
+    QTest::addColumn<bool>("translucent");
+    QTest::newRow("Translucent background disabled") << false;
+    QTest::newRow("Translucent background enabled") << true;
+}
+
+void tst_QOpenGLWidget::widgetWindowColorFormat()
+{
+    QFETCH(bool, translucent);
+
+    QOpenGLWidget w;
+    w.setAttribute(Qt::WA_TranslucentBackground, translucent);
+    w.setWindowTitle(QLatin1String(QTest::currentTestFunction()));
+    w.setFixedSize(16, 16);
+    w.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&w));
+
+    QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    QCOMPARE(w.format().redBufferSize(), ctx->format().redBufferSize());
+    QCOMPARE(w.format().greenBufferSize(), ctx->format().greenBufferSize());
+    QCOMPARE(w.format().blueBufferSize(), ctx->format().blueBufferSize());
+}
+
 class StaticTextPainterWidget : public QOpenGLWidget
 {
 public: