diff --git a/lib/proto.c b/lib/proto.c
index 3976e98b5..f798ece05 100644
--- a/lib/proto.c
+++ b/lib/proto.c
@@ -433,7 +433,7 @@ send_file_cancellation (guestfs_h *g)
 static int
 send_file_complete (guestfs_h *g)
 {
-  char buf[1];
+  char buf[1] = { '\0' };
   return send_file_chunk (g, 0, buf, 0);
 }