diff -r cc75c76972ee -r c0432d11811c src/gui/image/qimage.cpp
--- a/src/gui/image/qimage.cpp	Wed Apr 21 12:15:23 2010 +0300
+++ b/src/gui/image/qimage.cpp	Wed Apr 21 20:15:53 2010 +0300
@@ -118,8 +118,8 @@
     return &image.d->colortable;
 }
 
-extern int qt_defaultDpiX();
-extern int qt_defaultDpiY();
+Q_GUI_EXPORT extern int qt_defaultDpiX();
+Q_GUI_EXPORT extern int qt_defaultDpiY();
 
 QBasicAtomicInt qimage_serial_number = Q_BASIC_ATOMIC_INITIALIZER(1);
 
@@ -5667,7 +5667,11 @@
 
     detach();
 
-    *this = convertToFormat(QImage::Format_ARGB32_Premultiplied);
+    QImage converted = convertToFormat(QImage::Format_ARGB32_Premultiplied);
+    if (!converted.isNull())
+        *this = converted;
+    else
+        return;
 
     // Slight optimization since alphachannels are returned as 8-bit grays.
     if (alphaChannel.d->depth == 8 && alphaChannel.isGrayscale()) {