RHEL 6 DHCP - UEFI and Windows Deployment Server issue

[JeremyNguyen]

I am running a DHCP service on Red Hat Enterprise Linux 6.6 and have Windows Deployment Server deployed on the Legacy BIOS PXE Menu. I am trying to deploy UEFI (booting into grub.cfg) but I am running into this issue:
My syntax where UEFI is not working but WDS is working in /etc/dhcp/dhcpd.conf -

#Windows WDS
option space PXE;
option PXE.mtftp-ip code 1 = ip-address;
option PXE.mtftp-cport code 2 = unsigned integer 16;
option PXE.mtftp-sport code 3 = unsigned integer 16;
option PXE.mtftp-tmout code 4 = unsigned integer 8;
option PXE.mtftp-delay code 5 = unsigned integer 8;
option PXE.discovery-control code 6 = unsigned integer 8;
option PXE.discovery-mcast-addr code 7 = ip-address;

>option arch code 93 = unsigned integer 16;

>class "PXE" {
match if substring(option vendor-class-identifier, 0, 9) = "PXEClient";
vendor-option-space PXE;
option PXE.mtftp-ip 0.0.0.0;
next-server XX.X.X.X;
if option arch = 00:07 {
filename "pxelinux/BOOTX64.EFI";
} else {
filename "pxelinux.0";
}
option vendor-class-identifier "PXEClient";

My syntax to get UEFI working in /etc/dhcp/dhcpd.conf -

#Windows WDS
option space PXE;
option PXE.mtftp-ip code 1 = ip-address;
option PXE.mtftp-cport code 2 = unsigned integer 16;
option PXE.mtftp-sport code 3 = unsigned integer 16;
option PXE.mtftp-tmout code 4 = unsigned integer 8;
option PXE.mtftp-delay code 5 = unsigned integer 8;
option PXE.discovery-control code 6 = unsigned integer 8;
option PXE.discovery-mcast-addr code 7 = ip-address;

>option arch code 93 = unsigned integer 16;

>class "PXE" {
match if substring(option vendor-class-identifier, 0, 9) = "PXEClient";
vendor-option-space PXE;
option PXE.mtftp-ip 0.0.0.0;
next-server XX.X.X.X;
if option arch = 00:07 {
filename "pxelinux/BOOTX64.EFI";
} else {
filename "pxelinux.0";
}
#option vendor-class-identifier "PXEClient";

When I comment out the line "option vendor-class-identifier "PXEClient";", my Windows Deployment Server stops working but UEFI works. When I uncomment that line, Windows Deployment Server works but UEFI doesn't.