diff --git a/libexec/tftpd/tftpd.8 b/libexec/tftpd/tftpd.8
index 41e0a92a37f0..ec3ece5fc6a0 100644
--- a/libexec/tftpd/tftpd.8
+++ b/libexec/tftpd/tftpd.8
@@ -192,3 +192,8 @@ and the
 .Fl c
 option was introduced in
 .Fx 5.0 .
+.Sh BUGS
+Files larger than 33488896 octets (65535 blocks) cannot be transferred
+without client and server supporting blocksize negotiation (RFC1783).
+.Pp
+Many tftp clients will not transfer files over 16744448 octets (32767 blocks).
diff --git a/libexec/tftpd/tftpd.c b/libexec/tftpd/tftpd.c
index f0f0ca43ddb1..f219f081bf42 100644
--- a/libexec/tftpd/tftpd.c
+++ b/libexec/tftpd/tftpd.c
@@ -501,7 +501,7 @@ xmitfile(pf)
 	struct tftphdr *dp, *r_init();
 	register struct tftphdr *ap;    /* ack packet */
 	register int size, n;
-	volatile int block;
+	volatile unsigned short block;
 
 	signal(SIGALRM, timer);
 	dp = r_init();
@@ -571,7 +571,7 @@ recvfile(pf)
 	struct tftphdr *dp, *w_init();
 	register struct tftphdr *ap;    /* ack buffer */
 	register int n, size;
-	volatile int block;
+	volatile unsigned short block;
 
 	signal(SIGALRM, timer);
 	dp = w_init();
diff --git a/usr.bin/tftp/tftp.1 b/usr.bin/tftp/tftp.1
index 15eab9898f50..0c75272fdb34 100644
--- a/usr.bin/tftp/tftp.1
+++ b/usr.bin/tftp/tftp.1
@@ -167,6 +167,9 @@ protocol, the remote site will probably have some
 sort of file-access restrictions in place.  The
 exact methods are specific to each site and therefore
 difficult to document here.
+.Pp
+Files larger than 33488896 octets (65535 blocks) cannot be transferred
+without client and server supporting blocksize negotiation (RFC1783).
 .Sh HISTORY
 The
 .Nm
diff --git a/usr.bin/tftp/tftp.c b/usr.bin/tftp/tftp.c
index 9dc00afeddba..e7dc82473802 100644
--- a/usr.bin/tftp/tftp.c
+++ b/usr.bin/tftp/tftp.c
@@ -96,7 +96,8 @@ xmitfile(fd, name, mode)
 	register struct tftphdr *ap;	   /* data and ack packets */
 	struct tftphdr *r_init(), *dp;
 	register int n;
-	volatile int block, size, convert;
+	volatile unsigned short block;
+	volatile int size, convert;
 	volatile unsigned long amount;
 	struct sockaddr_in from;
 	int fromlen;
@@ -201,7 +202,8 @@ recvfile(fd, name, mode)
 	register struct tftphdr *ap;
 	struct tftphdr *dp, *w_init();
 	register int n;
-	volatile int block, size, firsttrip;
+	volatile unsigned short block;
+	volatile int size, firsttrip;
 	volatile unsigned long amount;
 	struct sockaddr_in from;
 	int fromlen;