diff --git a/ospf6d/ospf6_intra.c b/ospf6d/ospf6_intra.c
index 1ef0b53..6606c96 100644
--- a/ospf6d/ospf6_intra.c
+++ b/ospf6d/ospf6_intra.c
@@ -234,9 +234,9 @@
 
       /* Multiple Router-LSA instance according to size limit setting */
       if ( (oa->router_lsa_size_limit != 0)
-          && ((caddr_t) lsdesc + sizeof (struct ospf6_router_lsdesc) -
-	      /* XXX warning: comparison between signed and unsigned */
-              (caddr_t) buffer > oa->router_lsa_size_limit))
+          && ((size_t)((char *)lsdesc - buffer)
+                 + sizeof (struct ospf6_router_lsdesc)
+               > oa->router_lsa_size_limit))
         {
           if ((caddr_t) lsdesc == (caddr_t) router_lsa +
                                   sizeof (struct ospf6_router_lsa))