diff --git a/ripngd/ripngd.c b/ripngd/ripngd.c
index a7254bc..edf959f 100644
--- a/ripngd/ripngd.c
+++ b/ripngd/ripngd.c
@@ -2992,7 +2992,7 @@
 }
 
 void
-ripng_routemap_update (char *unused)
+ripng_routemap_update (const char *unused)
 {
   struct interface *ifp;
   struct listnode *node;