How can I resolve this error in keil MDKv5 ? security(project name).axf: Error: L6200E: Symbol SystemCoreClockUpdate multiply defined (by system_stm32f4xx_1.o and system_stm32f4xx.o).

Hi

I am getting this error for my discovery board (STM32F407vgtx).

Please suggest me the proper solution.

Thanks 

Gulfan Ahamad