diff --git a/config.h b/config.h
index 6515d0d..117e478 100644
--- a/config.h
+++ b/config.h
@@ -37,6 +37,6 @@
 /* define HAVE_IP_MREQN to use struct ip_mreqn instead of struct ip_mreq
  * for setsockopt(IP_MULTICAST_IF). Available with Linux 2.4+,
  * FreeBSD, etc. */
-/*#define HAVE_IP_MREQN*/
+#define HAVE_IP_MREQN
 
 #endif