diff --git a/ospf6d/ospf6_interface.h b/ospf6d/ospf6_interface.h
index 878c29e..cf758c0 100644
--- a/ospf6d/ospf6_interface.h
+++ b/ospf6d/ospf6_interface.h
@@ -76,6 +76,9 @@
   /* OSPF6 Interface flag */
   char flag;
 
+  /* MTU mismatch check */
+  u_char mtu_ignore;
+
   /* Decision of DR Election */
   u_int32_t drouter;
   u_int32_t bdrouter;