identifier undefined in rtx_lib. how to resolve this?

C:\Keil\ARM\RV31\INC\RTX_lib.c(54): error:  #20: identifier "OS_TIMER" is undefined
C:\Keil\ARM\RV31\INC\RTX_lib.c(126): error:  #20: identifier "OS_TVAL" is undefined
C:\Keil\ARM\RV31\INC\RTX_lib.c(135): error:  #20: identifier "OS_TOVF" is undefined

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