kernel bbappend files failed to triggler build updated in kirkstone branch, could be bugs?



I have a kernel bbappend file which can update patch files but cannot
not update a defconfig file when the files are changed.

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"

SRC_URI:append = "file://0001_wifi.patch \
file://0001-kernel-mtd.patch \
file://defconfig \

All files are in files directory, if I change a patch file, it can
trigger the build, but if I change the defconfig file, it could not
trigger the new build. Is it a bug in the kirkstone branch?

Thank you.

Kind regards,