diff -r fcece45ef507 -r 79de32ba3296 src/gui/image/qpixmap_x11.cpp
--- a/src/gui/image/qpixmap_x11.cpp	Mon May 03 13:17:34 2010 +0300
+++ b/src/gui/image/qpixmap_x11.cpp	Fri May 14 16:40:13 2010 +0300
@@ -383,7 +383,7 @@
             return has;
         // Will implicitly also check format and return quickly for opaque types...
         checked = true;
-        has = const_cast<QImage *>(image)->data_ptr()->checkForAlphaPixels();
+        has = image->isNull() ? false : const_cast<QImage *>(image)->data_ptr()->checkForAlphaPixels();
         return has;
     }