diff --git a/net/quagga/Makefile b/net/quagga/Makefile
index 9ad6ceb95..27dbd6222 100644
--- a/net/quagga/Makefile
+++ b/net/quagga/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}; \