Not grammatically correct, Amos? It is grammatically "correct", because it is a long standing accepted standard useage in the spoken language of a particular area--when you move out of the area, it isn't appropriate any more because it tags you--

Correct grammar is really a matter of politics-when you use certain grammatical structures, you are tagged--you become associated, in the mind of your listeners/readers, with the other people who use those same structures--