grub has wrong path for Windows boot

[sean darcy]

I'm on FC31, dual boot.

os-prober finds the Windows efi boot partition. /dev/nvme0n1p1

sudo mount /dev/nvme0n1p1 nvme0n1p1/
$ ls nvme0n1p1/EFI/Microsoft/Boot/bootmgfw.efi
nvme0n1p1/EFI/Microsoft/Boot/bootmgfw.efi

But boot from the grub menu fails:

'/efi/Microsoft/Boot/bootmgfw.efi' not found

because the grub path use lower case efi, while the the actual path has 
it capitalized.

Where does grub store the path it uses for the Windows boot manager ?

sean