Undefined symbol Driver_USARTn (referred from usbd_user_cdc_acm_9.o)

Hello all!

I am trying to include a USB funcionality to my project. I am working with the scripts that KEIL give, but when I build the project I have the following report:

.\Objects\DataRain_EDM.axf: Error: L6218E: Undefined symbol Driver_USARTn (referred from usbd_user_cdc_acm_0.o).
Not enough information to list image symbols.
Not enough information to list load addresses in the image map.
Finished: 2 information, 0 warning and 1 error messages.

I have tried to modify the Linker properties and it has not worked.