diff -ruN smeserver-tftp-server-1.2.old/root/var/service/tftpd/run smeserver-tftp-server-1.2/root/var/service/tftpd/run
--- smeserver-tftp-server-1.2.old/root/var/service/tftpd/run	2018-03-29 10:49:17.177967160 +0200
+++ smeserver-tftp-server-1.2/root/var/service/tftpd/run	2018-11-12 16:48:14.583596187 +0100
@@ -24,7 +24,19 @@
     TFTPD_DIRECTORY=$(/sbin/e-smith/db configuration getprop tftpd directory);
     TFTPD_REFUSE=$(/sbin/e-smith/db configuration getprop tftpd refuse);
     TFTPD_BLKSIZE=$(/sbin/e-smith/db configuration getprop tftpd blksize);
-    
+
+    # If BLKSIZE is set
+    if [ ! -z $TFTPD_BLKSIZE ]; then
+    #echo "Block size $TFTPD_BLKSIZE"
+        if   [ "$TFTPD_BLKSIZE" -le "512" ] ; then
+            TFTPD_BLKSIZE=1500;
+        elif [ "$TFTPD_BLKSIZE" -ge "65464" ] ; then
+            TFTPD_BLKSIZE=65464;
+        fi
+        #echo "Now we have $TFTPD_BLKSIZE"
+    fi
+    #echo "Block size is $TFTPD_BLKSIZE"
+
     TFTPD_ACCESS_SETTING="127.0.0.1";
     if [ $TFTPD_ACCESS == "public" ]; then
 	TFTPD_ACCESS_SETTING="0.0.0.0";