WDR4300 backup on ath79

Hello!

I wantet to test ath79 on my WDR4300 but i can't flash my backup.

ar71xx:

cat /proc/mtd | grep firmware
mtd5: 007d0000 00010000 "firmware"
cat /dev/mtd5 > /tmp/fw.bin
sysupgrade -T /tmp/fw.bin
Image metadata not found

ath79:

cat /proc/mtd | grep firmware
mtd1: 007d0000 00010000 "firmware"
cat /dev/mtd1 > /tmp/fw.bin
sysupgrade -T /tmp/fw.bin
Image metadata not found
Use sysupgrade -F to override this check when downgrading or flashing to vendor firmware
Image check 'fwtool_check_image' failed.

Any suggestions?

Robert