Grub2 cannot detect multiboot header x64-msvc build

I'm trying to boot FreeLdr x64-msvc with grub2 (2.06) and it's failing. Attached a script to check if FreeLdr.sys has valid multiboot header. For any x86 build it outputs OK, but for x64 (e.g. 0.4.15-dev-5059-g87f2950-x64-msvc-win-dbg) it fails.
Also I find multiboot magic 0x1BADB002 at freeldr's x86 version, it's located at 0x0A00 offset, but for x64 the offset has another value 0x0000F000