[yocto] [meta-xilinx] PREFERRED_VERSION_linux-libc-headers = "3.6" getting ignored

[Elvis Dowson]

Hi,
       In my zynq-7-default-versions.inc file, I have the following definitions for preferred versions

PREFERRED_VERSION_virtual/kernel ?= "3.6"
PREFERRED_VERSION_linux-libc-headers = "3.6"
PREFERRED_VERSION_u-boot = "2012.10"

However, when I build core-image-minimal, PREFERRED_VERSION_linux-libc-headers = "3.6" gets ignored and it goes ahead and builds linux-libc-headers_3.8.bb

Is it only effective if specified in the local.conf file?

Elvis Dowson