diff --git a/lib/if.c b/lib/if.c
index de3f641..4ba973a 100644
--- a/lib/if.c
+++ b/lib/if.c
@@ -422,7 +422,7 @@
 
 /* For debugging */
 static void
-if_dump (struct interface *ifp)
+if_dump (const struct interface *ifp)
 {
   struct listnode *node;
   struct connected *c;