diff --git a/bin/cros_make_image_bootable b/bin/cros_make_image_bootable
index cc9f79a243..476021b58d 100755
--- a/bin/cros_make_image_bootable
+++ b/bin/cros_make_image_bootable
@@ -273,7 +273,7 @@ make_image_bootable() {
   esp_size=$((esp_size * 512))  # sectors to bytes
   local bootloader_to_flags="--to_offset=${esp_offset} --to_size=${esp_size}"
 
-  if [ "${FLAGS_arch}" = "x86" -o "${FLAGS_arch}" = "amd64" ]; then
+  if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64" ]]; then
     # Use the kernel partition to acquire configuration flags.
     kernel_part="--kernel_partition='${FLAGS_output_dir}/vmlinuz.image'"
     # Install syslinux on the EFI System Partition.
diff --git a/build_kernel_image.sh b/build_kernel_image.sh
index 8756b820a9..a22a73d5b3 100755
--- a/build_kernel_image.sh
+++ b/build_kernel_image.sh
@@ -148,7 +148,7 @@ EOF
 WORK="${WORK} ${FLAGS_working_dir}/boot.config"
 info "Emitted cross-platform boot params to ${FLAGS_working_dir}/boot.config"
 
-if [ "${FLAGS_arch}" = "x86" -o "${FLAGS_arch}" = "amd64" ]; then
+if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64" ]]; then
   # Legacy BIOS will use the kernel in the rootfs (via syslinux), as will
   # standard EFI BIOS (via grub, from the EFI System Partition). Chrome OS
   # BIOS will use a separate signed kernel partition, which we'll create now.
diff --git a/build_library/build_gpt.sh b/build_library/build_gpt.sh
index 60f42479ad..7c914e80d9 100755
--- a/build_library/build_gpt.sh
+++ b/build_library/build_gpt.sh
@@ -47,7 +47,7 @@ build_gpt() {
   local pmbr_img
   if [ "$ARCH" = "arm" ]; then
     pmbr_img=/dev/zero
-  elif [ "$ARCH" = "x86" -o "$ARCH" = "amd64" ]; then
+  elif [[ "$ARCH" = "x86" || "$ARCH" = "amd64" ]]; then
     pmbr_img=$(readlink -f /usr/share/syslinux/gptmbr.bin)
   else
     error "Unknown architecture: $ARCH"
diff --git a/build_library/create_legacy_bootloader_templates.sh b/build_library/create_legacy_bootloader_templates.sh
index 3b8ff39694..2614bb1cf7 100755
--- a/build_library/create_legacy_bootloader_templates.sh
+++ b/build_library/create_legacy_bootloader_templates.sh
@@ -55,7 +55,7 @@ verity_common="${verity_common} dm_verity.dev_wait=${dev_wait}"
 # Populate the x86 rootfs to support legacy and EFI bios config templates.
 # The templates are used by the installer to populate partition 12 with
 # the correct bootloader configuration.
-if [ "${FLAGS_arch}" = "x86" -o "${FLAGS_arch}" = "amd64"  ]; then
+if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64"  ]]; then
   # TODO: For some reason the /dev/disk/by-uuid is not being generated by udev
   # in the initramfs. When we figure that out, switch to root=UUID=${UUID}.
   sudo mkdir -p ${FLAGS_to}
diff --git a/update_bootloaders.sh b/update_bootloaders.sh
index 39a077fee9..27a5a8e0be 100755
--- a/update_bootloaders.sh
+++ b/update_bootloaders.sh
@@ -189,7 +189,7 @@ cleanup() {
 trap cleanup EXIT
 sudo mount "${ESP_DEV}" "${ESP_FS_DIR}"
 
-if [ "${FLAGS_arch}" = "x86" -o "${FLAGS_arch}" = "amd64" ]; then
+if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64" ]]; then
   # Populate the EFI bootloader configuration
   sudo mkdir -p "${ESP_FS_DIR}/efi/boot"
   sudo cp "${FLAGS_from}"/efi/boot/bootx64.efi \