Nexus 6 error: update package missing system.img

[AC Question]

target reported max download size of 536870912 bytes
sending 'bootloader' (4071 KB)...
OKAY [ 0.131s]
writing 'bootloader'...
(bootloader) flashing partition ...
(bootloader) This may take a few seconds if a
(bootloader) different partition table is being
(bootloader) flashed since we need to backup
(bootloader) and restore a few partitions
(bootloader) Flashing primary GPT image...
(bootloader) Flashing backup GPT image...
(bootloader) flashing aboot ...
(bootloader) flashing sbl1 ...
(bootloader) flashing rpm ...
(bootloader) flashing tz ...
(bootloader) flashing sdi ...
(bootloader) flashing logo ...
OKAY [ 0.632s]
finished. total time: 0.764s
rebooting into bootloader...
OKAY [ 0.001s]
finished. total time: 0.001s
target reported max download size of 536870912 bytes
sending 'radio' (115507 KB)...
OKAY [ 3.625s]
writing 'radio'...
(bootloader) flashing modem ...
(bootloader) flashing mdm1m9kefs1 ...
(bootloader) flashing mdm1m9kefs2 ...
(bootloader) flashing mdm1m9kefs3 ...
(bootloader) flashing versions ...
OKAY [ 1.526s]
finished. total time: 5.153s
rebooting into bootloader...
OKAY [ 0.001s]
finished. total time: 0.001s
target reported max download size of 536870912 bytes
archive does not contain 'boot.sig'
archive does not contain 'recovery.sig'
failed to allocate 1513810096 bytes
error: update package missing system.img
Press any key to exit...