+// there is no src/{msw,mgl}/popupwin.cpp to put this in, so we do it here - BTW we
+// probably could do it for all ports here just as well
+#if defined(__WXMSW__) || defined(__WXMGL__)
+ IMPLEMENT_DYNAMIC_CLASS(wxPopupWindow, wxWindow)
+#endif // __WXMSW__
+
+IMPLEMENT_DYNAMIC_CLASS(wxPopupTransientWindow, wxPopupWindow)
+
+#if wxUSE_COMBOBOX && defined(__WXUNIVERSAL__)
+ IMPLEMENT_DYNAMIC_CLASS(wxPopupComboWindow, wxPopupTransientWindow)
+#endif
+