diff --git a/CHANGES b/CHANGES
index cdb9a2e..5238089 100644
--- a/CHANGES
+++ b/CHANGES
@@ -6,6 +6,9 @@ Changes in 5.1:
 
 	Build fixes.
 
+	Fix handling of block number wraparound after a successful
+	options negotiation.
+
 
 Changes in 5.0:
 	Try to on platforms with getaddrinfo() without AI_ADDRCONFIG or
diff --git a/tftpd/recvfrom.c b/tftpd/recvfrom.c
index 389ba82..3ee5642 100644
--- a/tftpd/recvfrom.c
+++ b/tftpd/recvfrom.c
@@ -245,7 +245,8 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
 
 int
 myrecvfrom(int s, void *buf, int len, unsigned int flags,
-           struct sockaddr *from, int *fromlen, union sock_addr *myaddr)
+           struct sockaddr *from, socklen_t * fromlen,
+           union sock_addr *myaddr)
 {
     /* There is no way we can get the local address, fudge it */
 
diff --git a/tftpd/tftpd.c b/tftpd/tftpd.c
index 1f946f6..c122d61 100644
--- a/tftpd/tftpd.c
+++ b/tftpd/tftpd.c
@@ -1648,6 +1648,10 @@ static void tftp_recvfile(const struct formats *pf, struct tftphdr *oap, int oac
             ap->th_opcode = htons((u_short) ACK);
             ap->th_block = htons((u_short) block);
             acksize = 4;
+            /* If we're sending a regular ACK, that means we have successfully
+             * sent the OACK. Clear oap so that we won't try to send another
+             * OACK when the block number wraps back to 0. */
+            oap = NULL;
         }
         if (!++block)
 	  block = rollover_val;