diff --git a/ospf6d/ospf6_proto.c b/ospf6d/ospf6_proto.c
index 5b47cf8..584382a 100644
--- a/ospf6d/ospf6_proto.c
+++ b/ospf6d/ospf6_proto.c
@@ -70,7 +70,7 @@
 }
 
 void
-ospf6_options_printbuf (char *options, char *buf, int size)
+ospf6_options_printbuf (u_char *options, char *buf, int size)
 {
   char *dc, *r, *n, *mc, *e, *v6;
   dc = (OSPF6_OPT_ISSET (options, OSPF6_OPT_DC) ? "DC" : "--");