grub switching from http to tftp?

[Avi Deitcher]

I am booting a system:

1. UEFI PXE, which then downloads ipxe.efi via tftp
2. Then downloads ipxe.efi.cfg via http (as configured in dnsmasq)
3. ipxe.cfg is set to `chain http://myserver/EFI/BOOT/BOOTX64.EFI` (which
is grub) over http
4. Which tries to download tftp://myserver/EFI/BOOT/grub.cfg (over tftp
rather than http)

Why does it switch to http to get grub.cfg when grub itself (and ipxe.cfg)
were downloaded over http? I forced it into grub shell:

echo $prefix
(tftp,192.168.1.10)/EFI/BOOT

What am I doing incorrect?
Thanks in advance