diff --git a/config/sources/families/include/rockchip64_common.inc b/config/sources/families/include/rockchip64_common.inc
index 37b76d4cb3..65f30be64e 100644
--- a/config/sources/families/include/rockchip64_common.inc
+++ b/config/sources/families/include/rockchip64_common.inc
@@ -14,7 +14,7 @@ BOOTENV_FILE='rockchip64.txt'
 UBOOT_TARGET_MAP=";;idbloader.bin uboot.img trust.bin"
 BOOTDELAY=0
 OVERLAY_PREFIX='rockchip'
-SERIALCON=${SERIALCON:=$([ $BRANCH == "legacy" ] && echo "ttyFIQ0:1500000" || echo "ttyS2:1500000")}
+SERIALCON=${SERIALCON:=$([ "${BRANCH}" == "legacy" ] && echo "ttyFIQ0:1500000" || echo "ttyS2:1500000")}
 GOVERNOR="ondemand"
 ATFPATCHDIR='atf-rockchip64'
 BOOTPATCHDIR="${BOOTPATCHDIR:-"u-boot-rockchip64"}"