diff --git a/net/tftp.c b/net/tftp.c
index 3e99e73..89be32a 100644
--- a/net/tftp.c
+++ b/net/tftp.c
@@ -249,6 +249,8 @@ static void show_block_marker(void)
 	if (tftp_tsize) {
 		ulong pos = tftp_cur_block * tftp_block_size +
 			tftp_block_wrap_offset;
+		if (pos > tftp_tsize)
+			pos = tftp_tsize;
 
 		while (tftp_tsize_num_hash < pos * 50 / tftp_tsize) {
 			putc('#');