diff --git a/build_image b/build_image
index 8763041a72..3a26baacc0 100755
--- a/build_image
+++ b/build_image
@@ -150,8 +150,8 @@ EXTRA_USE=""
 if [ "${FLAGS_factory_install}" -eq "${FLAGS_TRUE}" ] ; then
   # Factory install needs to have the kernel initrmafs enabled,
   # and the factory installer added.
-  EXTRA_PACKAGES="chromeos-base/chromeos-factoryinstall"
-  EXTRA_USE="initramfs"
+  EXTRA_PACKAGES="${EXTRA_PACKAGES} chromeos-base/chromeos-factoryinstall"
+  EXTRA_USE="${EXTRA_USE} initramfs"
 fi
 
 # Freshen kernel with correct USE flags. This is a noop if we have