Why doesn't U-Boot disable the console output

Forum: Bootloader
embLin 
I have this system which is accessed by a serial Debug Port. I want to
disable all of the output, that was made during the U-Boot boot. Therefore
there is the

    setenv silent 1

parameter, which i put into the BOOTCMD string like:

    #define CONFIG_BOOTCOMMAND " setenv silent 1;" \

    "bootm "

and there is the

    #define CONFIG_SILENT_CONSOLE

command, neither one is working (the lines printed out are still the same
and the boot time didn't change). Does somebody see the error ?