diff --git a/lib/table.h b/lib/table.h
index ab7eb68..2ffd79b 100644
--- a/lib/table.h
+++ b/lib/table.h
@@ -148,9 +148,9 @@
 extern struct route_node *route_next_until (struct route_node *,
                                             struct route_node *);
 extern struct route_node *route_node_get (struct route_table *const,
-                                          struct prefix *);
+                                          const struct prefix *);
 extern struct route_node *route_node_lookup (const struct route_table *,
-                                             struct prefix *);
+                                             const struct prefix *);
 extern struct route_node *route_lock_node (struct route_node *node);
 extern struct route_node *route_node_match (const struct route_table *,
                                             const struct prefix *);