Compiler warnings fixes.
diff --git a/isisd/isis_tlv.c b/isisd/isis_tlv.c
index 70b3c17..c859ef0 100644
--- a/isisd/isis_tlv.c
+++ b/isisd/isis_tlv.c
@@ -881,7 +881,7 @@
 }
 
 int
-tlv_add_authinfo (char auth_type, char auth_len, char *auth_value,
+tlv_add_authinfo (char auth_type, char auth_len, u_char *auth_value,
 		  struct stream *stream)
 {
   u_char value[255];