diff --git a/net/tftp.c b/net/tftp.c
index 6d333d5..2e06808 100644
--- a/net/tftp.c
+++ b/net/tftp.c
@@ -281,7 +281,7 @@ static void update_block_number(void)
 	 * number of 0 this means that there was a wrap
 	 * around of the (16 bit) counter.
 	 */
-	if (TftpBlock == 0) {
+	if (TftpBlock == 0 && TftpLastBlock != 0) {
 		TftpBlockWrap++;
 		TftpBlockWrapOffset += TftpBlkSize * TFTP_SEQUENCE_SIZE;
 		TftpTimeoutCount = 0; /* we've done well, reset thhe timeout */