How to set the Code auto-complete don't Case Sensitive in QtCreator?

when i edit code in QtQcreator,Often used auto-complete or auto-Information Tips.
I find it is case-sensitive restriction,eg:
type [ QDir ] ,It can prompt [ QDirModel ];
type [ Qdir ] ,It can not prompt any information.

I Hope it can do work at every Environment,Because My English is poor and i' am a Qt Beginners.
Sometimes I do not know how the spelling of the key-word.

Options->Text Editor->Completion. Untick Case-sensitive completion.

Thanks very very very much !