diff --git a/libwifi/Makefile b/libwifi/Makefile
index 258fb0978..33b6a911c 100644
--- a/libwifi/Makefile
+++ b/libwifi/Makefile
@@ -61,7 +61,7 @@ else
 endif
 
 ifneq ($(CONFIG_PACKAGE_kmod-mt7915e_en7523),)
-  TARGET_CFLAGS=-DMT7915_VENDOR_EXT
+  TARGET_CFLAGS +=-DMT7915_VENDOR_EXT
 endif
 
 PKG_BUILD_DEPENDS:=PACKAGE_kmod-mt7915e_en7523:mt76_en7523