diff --git a/src/vty/buffer.c b/src/vty/buffer.c
index def2f52..e0abe81 100644
--- a/src/vty/buffer.c
+++ b/src/vty/buffer.c
@@ -299,7 +299,7 @@
 				zlog_warn("%s: growing iov array to %d; "
 					  "width %d, height %d, size %lu",
 					  __func__, iov_alloc, width, height,
-					  (u_long) b->size);
+					  (unsigned long) b->size);
 				iov =
 				    XREALLOC(MTYPE_TMP, iov,
 					     iov_alloc * sizeof(*iov));