It's not incorrect, just might cause trouble on particular combination of methods and classes AFAIK the problem stems from two sources - from the way Python garbage collection works and from the problem that it does not necessarily know about object pointer ownership transfers than happen on Qt's level. Can't find anything descriptive on google right now, so you'll have to take my word for it Or remember this and when your first segfault appears, try the suggested change above and then ponder why it fixes the problem