diff --git a/boot/u-boot/u-boot.mk b/boot/u-boot/u-boot.mk
index 9eeea1d004..7b6b2ce632 100644
--- a/boot/u-boot/u-boot.mk
+++ b/boot/u-boot/u-boot.mk
@@ -77,7 +77,7 @@ $(U_BOOT_DIR)/.patched: $(U_BOOT_DIR)/.unpacked
 	toolchain/patch-kernel.sh $(U_BOOT_DIR) boot/u-boot \
 		u-boot-$(U_BOOT_VERSION)-\*.patch \
 		u-boot-$(U_BOOT_VERSION)-\*.patch.$(ARCH)
-ifneq ($(strip $(BR2_TARGET_UBOOT_CUSTOM_PATCH_DIR)),"")
+ifneq ($(call qstrip,$(BR2_TARGET_UBOOT_CUSTOM_PATCH_DIR)),)
 	toolchain/patch-kernel.sh $(U_BOOT_DIR) $(BR2_TARGET_UBOOT_CUSTOM_PATCH_DIR) u-boot-$(U_BOOT_VERSION)-\*.patch
 endif
 	touch $@