[U-Boot] start a second kernel/filesystem if first one is corrupted

To make a more stable system I want to put a second reduced linux (kernel/rootfs) onto flash memory. This should be boot automatically, if #1 fails for any reason. I tried to add this in bootcmd, but execution will be interuppted if the first bootm failes. Is there any chance to do so? (maybe it is even possible to compile this into bootloader, in case uboot environment gets corrupted/misconfigured)