diff --git a/zebra/interface.h b/zebra/interface.h
index 0f081f6..fe24604 100644
--- a/zebra/interface.h
+++ b/zebra/interface.h
@@ -38,11 +38,13 @@
 #define IF_ZEBRA_SHUTDOWN_ON     1
 
 /* Router advertisement feature. */
+#ifndef RTADV
 #if (defined(LINUX_IPV6) && (!defined(__GLIBC__) || defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1)) || defined(KAME)
   #ifdef HAVE_RTADV
     #define RTADV
   #endif
 #endif
+#endif
 
 #ifdef RTADV
 /* Router advertisement parameter.  From RFC4861, RFC6275 and RFC4191. */