diff --git a/Makefile b/Makefile
index 9ad6ceb..27dbd62 100644
--- a/Makefile
+++ b/Makefile
@@ -181,7 +181,7 @@ CONFIGURE_ARGS+= \
 	$(call autoconf_bool,CONFIG_PACKAGE_quagga-vtysh,vtysh) \
 
 MAKE_FLAGS += \
-	CFLAGS="$(TARGET_CFLAGS) -D_GNU_SOURCE"
+	CFLAGS="$(TARGET_CFLAGS) -D_GNU_SOURCE -std=gnu99"
 
 define Build/Configure
 	(cd $(PKG_BUILD_DIR); rm -rf config.{cache,status}; \