diff --git a/build_image b/build_image
index d6e2cba551..16227982cc 100755
--- a/build_image
+++ b/build_image
@@ -24,6 +24,8 @@ DEFINE_string board "${DEFAULT_BOARD}" \
   "The board to build an image for."
 DEFINE_boolean enable_rootfs_verification ${FLAGS_TRUE} \
   "Default all bootloaders to use kernel-based root fs integrity checking."
+DEFINE_string base_pkg "coreos-base/coreos" \
+  "The base portage package to base the build off of (only applies to prod images)"
 DEFINE_string output_root "${DEFAULT_BUILD_ROOT}/images" \
   "Directory in which to place image result directories (named by version)"
 DEFINE_string disk_layout "" \
@@ -161,7 +163,7 @@ if [[ "${CONTAINER}" -eq 1 ]]; then
 fi
 
 if [[ "${PROD_IMAGE}" -eq 1 ]]; then
-  create_prod_image ${COREOS_PRODUCTION_IMAGE_NAME} ${DISK_LAYOUT} ${FLAGS_group}
+  create_prod_image ${COREOS_PRODUCTION_IMAGE_NAME} ${DISK_LAYOUT} ${FLAGS_group} ${FLAGS_base_pkg}
   if [[ ${FLAGS_generate_update} -eq ${FLAGS_TRUE} ]]; then
     generate_update "${COREOS_PRODUCTION_IMAGE_NAME}" ${DISK_LAYOUT}
   elif [[ ${FLAGS_extract_update} -eq ${FLAGS_TRUE} ]]; then
diff --git a/build_library/prod_image_util.sh b/build_library/prod_image_util.sh
index e712665c8f..ce681557f2 100755
--- a/build_library/prod_image_util.sh
+++ b/build_library/prod_image_util.sh
@@ -29,6 +29,11 @@ create_prod_image() {
   local image_name="$1"
   local disk_layout="$2"
   local update_group="$3"
+  local base_pkg="$4"
+  if [ -z "${base_pkg}" ]; then
+    echo "did not get base package!"
+    exit 1
+  fi
 
   info "Building production image ${image_name}"
   local root_fs_dir="${BUILD_DIR}/rootfs"
@@ -40,7 +45,7 @@ create_prod_image() {
   # Install minimal GCC (libs only) and then everything else
   set_image_profile prod
   extract_prod_gcc "${root_fs_dir}"
-  emerge_to_image "${root_fs_dir}" coreos-base/coreos
+  emerge_to_image "${root_fs_dir}" "${base_pkg}"
   write_packages "${root_fs_dir}" "${BUILD_DIR}/${image_packages}"
 
   # Assert that if this is supposed to be an official build that the