diff --git a/src/plugins/platforms/windows/accessible/qwindowsaccessibility.cpp b/src/plugins/platforms/windows/accessible/qwindowsaccessibility.cpp
index 752b9e7c20..146b114389 100644
--- a/src/plugins/platforms/windows/accessible/qwindowsaccessibility.cpp
+++ b/src/plugins/platforms/windows/accessible/qwindowsaccessibility.cpp
@@ -169,7 +169,9 @@ void QWindowsAccessibility::notifyAccessibilityUpdate(QAccessibleEvent *event)
     // An event has to be associated with a window,
     // so find the first parent that is a widget and that has a WId
     QAccessibleInterface *iface = event->accessibleInterface();
-    QWindow *window = iface ? QWindowsAccessibility::windowHelper(iface) : 0;
+    if (!iface) // ### This should not happen, maybe make it an assert.
+        return;
+    QWindow *window = QWindowsAccessibility::windowHelper(iface);
     delete iface;
 
     if (!window) {
diff --git a/src/widgets/accessible/qaccessiblewidget.cpp b/src/widgets/accessible/qaccessiblewidget.cpp
index 5c8d3e3a57..2b8e1a7036 100644
--- a/src/widgets/accessible/qaccessiblewidget.cpp
+++ b/src/widgets/accessible/qaccessiblewidget.cpp
@@ -205,6 +205,7 @@ QAccessibleWidget::QAccessibleWidget(QWidget *w, QAccessible::Role role, const Q
 /*! \reimp */
 QWindow *QAccessibleWidget::window() const
 {
+    Q_ASSERT(widget());
     return widget()->windowHandle();
 }
 
@@ -343,6 +344,7 @@ QAccessibleWidget::relations(QAccessible::Relation match /*= QAccessible::AllRel
 /*! \reimp */
 QAccessibleInterface *QAccessibleWidget::parent() const
 {
+    Q_ASSERT(widget());
     QObject *parentWidget= widget()->parentWidget();
     if (!parentWidget)
         parentWidget = qApp;
@@ -352,6 +354,7 @@ QAccessibleInterface *QAccessibleWidget::parent() const
 /*! \reimp */
 QAccessibleInterface *QAccessibleWidget::child(int index) const
 {
+    Q_ASSERT(widget());
     QWidgetList childList = childWidgets(widget());
     if (index >= 0 && index < childList.size())
         return QAccessible::queryAccessibleInterface(childList.at(index));
diff --git a/tests/auto/other/qaccessibility/tst_qaccessibility.cpp b/tests/auto/other/qaccessibility/tst_qaccessibility.cpp
index f5f336ed64..ce8032e0c3 100644
--- a/tests/auto/other/qaccessibility/tst_qaccessibility.cpp
+++ b/tests/auto/other/qaccessibility/tst_qaccessibility.cpp
@@ -364,6 +364,24 @@ void tst_QAccessibility::eventTest()
     QVERIFY(QTestAccessibility::containsEvent(&hideEvent));
 
     delete button;
+
+    // Make sure that invalid events don't bring down the system
+    // these events can be in user code.
+    QWidget *widget = new QWidget();
+    QAccessibleEvent ev1(widget, QAccessible::Focus);
+    QAccessible::updateAccessibility(&ev1);
+
+    QAccessibleEvent ev2(widget, QAccessible::Focus);
+    ev2.setChild(7);
+    QAccessible::updateAccessibility(&ev2);
+    delete widget;
+
+    QObject *object = new QObject();
+    QAccessibleEvent ev3(widget, QAccessible::Focus);
+    QAccessible::updateAccessibility(&ev3);
+    delete object;
+
+    QTestAccessibility::clearEvents();
 }