diff --git a/xtables-addons/Makefile b/xtables-addons/Makefile
index 789082703..60fd21125 100644
--- a/xtables-addons/Makefile
+++ b/xtables-addons/Makefile
@@ -36,6 +36,7 @@ define Package/xtables-addons
 endef
 
 # uses GNU configure
+TARGET_CFLAGS += -std=c99 -D_GNU_SOURCE
 
 CONFIGURE_ARGS+= \
 	--with-kbuild="$(LINUX_DIR)" \