diff --git a/bin/cros_make_image_bootable b/bin/cros_make_image_bootable
index 2a89df9215..70d42c4c8f 100755
--- a/bin/cros_make_image_bootable
+++ b/bin/cros_make_image_bootable
@@ -232,6 +232,7 @@ make_image_bootable() {
     --arch=${FLAGS_arch} \
     --to="${bootloader_to}" \
     --from="${FLAGS_rootfs_mountpoint}"/boot \
+    --vmlinuz_boot_kernel="${FLAGS_rootfs_mountpoint}"/boot/vmlinuz-boot_kernel \
     --vmlinuz="${FLAGS_rootfs_mountpoint}"/boot/vmlinuz \
     ${bootloader_to_flags}
 
diff --git a/build_library/create_legacy_bootloader_templates.sh b/build_library/create_legacy_bootloader_templates.sh
index d20ca6a91c..796cf6ca81 100755
--- a/build_library/create_legacy_bootloader_templates.sh
+++ b/build_library/create_legacy_bootloader_templates.sh
@@ -72,6 +72,10 @@ if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64"  ]]; then
   cat <<EOF | sudo dd of="${GRUB_DIR}/menu.lst.A" 2>/dev/null
 timeout         0
 
+title           CoreOS bootengine
+root            (hd0,0)
+kernel          /syslinux/vmlinuz-boot_kernel ${common_args} root=gptprio: cros_legacy
+
 title           CoreOS A
 root            (hd0,0)
 kernel          /syslinux/vmlinuz.A ${common_args} root=${ROOTA} cros_legacy
@@ -82,12 +86,8 @@ kernel          /syslinux/vmlinuz.B ${common_args} root=${ROOTB} cros_legacy
 EOF
   info "Emitted ${GRUB_DIR}/menu.lst.A"
 
-  cat <<EOF | sudo dd of="${GRUB_DIR}/menu.lst.B" 2>/dev/null
-default         1
-EOF
-  sudo sh -c "cat ${GRUB_DIR}/menu.lst.A >> ${GRUB_DIR}/menu.lst.B"
+  sudo cp ${GRUB_DIR}/menu.lst.A ${GRUB_DIR}/menu.lst.B
   info "Emitted ${GRUB_DIR}/menu.lst.B"
-
   sudo cp ${GRUB_DIR}/menu.lst.A ${GRUB_DIR}/menu.lst
 
   # /boot/syslinux must be installed in partition 12 as /syslinux/.
@@ -97,9 +97,9 @@ EOF
   cat <<EOF | sudo dd of="${SYSLINUX_DIR}/syslinux.cfg" 2>/dev/null
 PROMPT 0
 TIMEOUT 0
+DEFAULT boot_kernel
 
-# the actual target
-include /syslinux/default.cfg
+include /syslinux/boot_kernel.cfg
 
 # coreos.A
 include /syslinux/root.A.cfg
@@ -109,15 +109,16 @@ include /syslinux/root.B.cfg
 EOF
   info "Emitted ${SYSLINUX_DIR}/syslinux.cfg"
 
-  # To change the active target, only this file needs to change.
-  cat <<EOF | sudo dd of="${SYSLINUX_DIR}/default.cfg" 2>/dev/null
-DEFAULT coreos.A
-EOF
-  info "Emitted ${SYSLINUX_DIR}/default.cfg"
-
   # Different files are used so that the updater can only touch the file it
   # needs to for a given change.  This will minimize any potential accidental
   # updates issues, hopefully.
+  cat <<EOF | sudo dd of="${SYSLINUX_DIR}/boot_kernel.cfg" 2>/dev/null
+label boot_kernel
+  menu label boot_kernel
+  kernel vmlinuz-boot_kernel
+  append ${common_args} root=gptprio: cros_legacy
+EOF
+  info "Emitted ${SYSLINUX_DIR}/boot_kernel.cfg"
   cat <<EOF | sudo dd of="${SYSLINUX_DIR}/root.A.cfg" 2>/dev/null
 label coreos.A
   menu label coreos.A
diff --git a/update_bootloaders.sh b/update_bootloaders.sh
index afe1bd95da..2144b180e7 100755
--- a/update_bootloaders.sh
+++ b/update_bootloaders.sh
@@ -32,6 +32,8 @@ DEFINE_integer to_size -1 \
   "Size in bytes of 'to' to use if it is a file. -1 is ignored. (Default: -1)"
 DEFINE_string vmlinuz "/tmp/vmlinuz" \
   "Path to the vmlinuz file to use (Default: /tmp/vmlinuz)"
+DEFINE_string vmlinuz_boot_kernel "/tmp/vmlinuz-boot_kernel" \
+  "Path to the vmlinuz-boot_kernel file to use (Default: /tmp/vmlinuz)"
 
 # Parse flags
 FLAGS "$@" || exit 1
@@ -108,6 +110,7 @@ if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64" ]]; then
   sudo cp -r "${FLAGS_from}"/syslinux/. "${ESP_FS_DIR}"/syslinux
 
   # Stage both kernels with the only one we built.
+  sudo cp -f "${FLAGS_vmlinuz_boot_kernel}" "${ESP_FS_DIR}"/syslinux/vmlinuz-boot_kernel
   sudo cp -f "${FLAGS_vmlinuz}" "${ESP_FS_DIR}"/syslinux/vmlinuz.A
   sudo cp -f "${FLAGS_vmlinuz}" "${ESP_FS_DIR}"/syslinux/vmlinuz.B