Compiler warnings fixes.
diff --git a/isisd/isis_pdu.c b/isisd/isis_pdu.c
index bf8c14f..436240e 100644
--- a/isisd/isis_pdu.c
+++ b/isisd/isis_pdu.c
@@ -334,7 +334,7 @@
   adj = circuit->u.p2p.neighbor;
   if (!adj)
     {
-      adj = isis_new_adj (hdr->source_id, "      ", 0, circuit);
+      adj = isis_new_adj (hdr->source_id, (u_char *) "      ", 0, circuit);
       if (adj == NULL)
 	return ISIS_ERROR;
       circuit->u.p2p.neighbor = adj;
@@ -1587,7 +1587,7 @@
   if (!adj)
     {
       /* 8.2.2 */
-      adj = isis_new_adj (sysid, "      ", 0, circuit);
+      adj = isis_new_adj (sysid, (u_char *) "      ", 0, circuit);
       if (adj == NULL)
 	return ISIS_ERROR;
 
@@ -1603,7 +1603,7 @@
       /* 8.2.2 a) 2) delete the adj */
       XFREE (MTYPE_ISIS_ADJACENCY, adj);
       /* 8.2.2 a) 3) create a new adj */
-      adj = isis_new_adj (sysid, "      ", 0, circuit);
+      adj = isis_new_adj (sysid, (u_char *) "      ", 0, circuit);
       if (adj == NULL)
 	return ISIS_ERROR;