Flashing an M1015 – Error code = 64 Failed to flash the image. Please retry recovery

I purchased an IBM M1015 to use as an HBA in my server. As part of that, I wanted to flash it with the IT firmware, however, I was getting errors, even when I used the original IBM firmware from their website:

C:\> megarec -cleanflash 0 M1000FW.ROM

MegaRAID HWR Controller Recovery tool. Version 01.01-004 February 05, 2010
Copyright (c) 2006-2008 LSI Corp.
Supports 1079 controller and its Successors


Erasing Flash Chip (8MB)....
 Completed: 100%
Flashing Image. Please wait...


Currently flashing component = BIOS
Programming Flash....
 Completed: 100%
Verifying the Flashed Data...


Currently flashing component = HIIM
Programming Flash....
 Completed: 100%
Verifying the Flashed Data...


Currently flashing component = APP
Error in downloading the image.
Error code = 64
Failed to flash the image. Please retry recovery

I’d never seen an M1015 before, at least not close up. Closer inspection of the card, however, revealed a code: FRU 46C8927. I know FRU” means “Field Replaceable Unit” i.e. something you can order as a replacement part. So I googled that code, and discovered that this was an IBM M5015, not an M1015. The M5015 cannot be used in IT mode, so I had to send it back.