diff --git a/Makefile b/Makefile
index 35685f8..d41abc6 100755
--- a/Makefile
+++ b/Makefile
@@ -662,7 +662,7 @@ EXTRA_CFLAGS += -DCONFIG_IOCTL_CFG80211 -DRTW_USE_CFG80211_STA_EVENT
 SUBARCH := $(shell uname -m | sed -e "s/i.86/i386/; s/ppc/powerpc/; s/armv.l/arm/; s/aarch64/arm64/;")
 ARCH ?= $(SUBARCH)
 CROSS_COMPILE ?=
-KVER  ?= $(shell if [[ -n ${NEW_VERSION} && ${FLAVOR} ]]; then echo ${NEW_VERSION}-${FLAVOR}; else uname -r; fi)
+KVER  ?= $(shell if [ -n "${NEW_VERSION}" ] && [ -n "${FLAVOR}" ]; then echo "${NEW_VERSION}-${FLAVOR}"; else uname -r; fi)
 KSRC := /lib/modules/$(KVER)/build
 MODDESTDIR := /lib/modules/$(KVER)/kernel/drivers/net/wireless/
 INSTALL_PREFIX :=