Upload .doc files

I can't upload .doc files .

Controller 

Code:

       $config['upload_path']          = './assets/uploads/atasamente/';
       $config['allowed_types']        = 'txt|xls|xlsx|doc|docx|pdf';
       $config['max_size']             = 10000;

        $this->load->library('upload', $config);

When trying to add a .doc file i get 

Code:

The filetype you are attempting to upload is not allowed.

Any info on this ?

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