3 files changed, 8 insertions, 3 deletions
diff --git a/src/gui/dialogs/qwizard.cpp b/src/gui/dialogs/qwizard.cpp
index 2c29ebf..b2ed983 100644
--- a/src/gui/dialogs/qwizard.cpp
+++ b/src/gui/dialogs/qwizard.cpp
@@ -1469,7 +1469,7 @@ void QWizardPrivate::handleAeroStyleChange()
         return; // prevent recursion
     inHandleAeroStyleChange = true;
 
-    vistaHelper->backButton()->disconnect();
+    vistaHelper->disconnectBackButton();
     q->removeEventFilter(vistaHelper);
 
     if (isVistaThemeEnabled()) {
@@ -1495,7 +1495,7 @@ void QWizardPrivate::handleAeroStyleChange()
         q->setMouseTracking(true); // ### original value possibly different
         q->unsetCursor(); // ### ditto
         antiFlickerWidget->move(0, 0);
-        vistaHelper->backButton()->hide();
+        vistaHelper->hideBackButton();
         vistaHelper->setTitleBarIconAndCaptionVisible(true);
     }
 
diff --git a/src/gui/dialogs/qwizard_win.cpp b/src/gui/dialogs/qwizard_win.cpp
index 64696de..8aad4af 100644
--- a/src/gui/dialogs/qwizard_win.cpp
+++ b/src/gui/dialogs/qwizard_win.cpp
@@ -239,9 +239,11 @@ void QVistaBackButton::paintEvent(QPaintEvent *)
 QVistaHelper::QVistaHelper(QWizard *wizard)
     : pressed(false)
     , wizard(wizard)
+    , backButton_(0)
 {
     is_vista = resolveSymbols();
-    backButton_ = new QVistaBackButton(wizard);
+    if (is_vista)
+        backButton_ = new QVistaBackButton(wizard);
 }
 
 QVistaHelper::~QVistaHelper()
@@ -310,6 +312,7 @@ void QVistaHelper::drawTitleBar(QPainter *painter)
             QRect(0, 0, wizard->width(), titleBarSize() + topOffset()),
             painter->paintEngine()->getDC());
 
+    Q_ASSERT(backButton_);
     const int btnTop = backButton_->mapToParent(QPoint()).y();
     const int btnHeight = backButton_->size().height();
     const int verticalCenter = (btnTop + btnHeight / 2);
diff --git a/src/gui/dialogs/qwizard_win_p.h b/src/gui/dialogs/qwizard_win_p.h
index cbb3b17..148be26 100644
--- a/src/gui/dialogs/qwizard_win_p.h
+++ b/src/gui/dialogs/qwizard_win_p.h
@@ -94,6 +94,8 @@ public:
     void resizeEvent(QResizeEvent *event);
     void paintEvent(QPaintEvent *event);
     QVistaBackButton *backButton() const { return backButton_; }
+    void disconnectBackButton() { if (backButton_) backButton_->disconnect(); }
+    void hideBackButton() { if (backButton_) backButton_->hide(); }
     void setWindowPosHack();
     QColor basicWindowFrameColor();
     enum VistaState { VistaAero, VistaBasic, Classic, Dirty };