Index: wxWidgets-2.9/src/msw/treectrl.cpp
===================================================================
--- wxWidgets-2.9/src/msw/treectrl.cpp	(revision 59398)
+++ wxWidgets-2.9/src/msw/treectrl.cpp	(working copy)
@@ -3309,7 +3309,7 @@
                 // similar to the ones from a "real" WM_KEYDOWN so that
                 // CreateKeyEvent() works correctly
                 return MSWHandleTreeKeyDownEvent(info->wVKey,
-                                                 wxIsAltDown() << 16);
+                                                 (wxIsAltDown() ? KF_ALTDOWN : 0) << 16);
             }
             break;