Sophos AV blocks server-sent events (SSE) on Mac OS X Yosemite

This took me a long time to figure out, so I'm posting here in the hopes that Google searches save the next vicitim, or that Sophos can do a fix.

I was testing a website with Server-Sent Events, i.e. EventSource events sent from a CGI script to my browser. Everything worked fine when both the server and browser was on my computer.  But when I tried to connect to the production browser, I was unable to recieve events; all browsers simply hung.  

After some testing, I realized it was Sophos.  Specifically, turning off "General / Web Protection / Block Malicious Downloads.." fixed the problem.

Sophos needs to be fixed so that it does not do blocking read/write of HTTP data with stream headers with

   Content-Type: text/event-stream

I'm not sure how it's blocking; it might be due to internal buffering sizes being too big or some other problem.

Here's a test site:

http://neutrino.otterbein.edu/~tagg/streamtest/test.cgi

This SHOULD print the time four times immediately, then print the time every 5 seconds thereafter. 

And here's the code sending it:

#!/usr/bin/perl -w
use IO::Handle qw( );  # For flush
use Time::HiRes qw(usleep nanosleep gettimeofday);

print "Content-Type: text/event-stream\r\n";
print "Cache-Control: no-cache\r\n";
print "\r\n";

print "data: " . localtime() . "\n\n";STDOUT->flush();

print "data: " . localtime() . "\n\n";STDOUT->flush();

print "data: " . localtime() . "\n\n";STDOUT->flush();

print "data: " . localtime() . "\n\n";STDOUT->flush();


while(1) {

  sleep(5);
print "data: " . localtime . "\n\n";
STDOUT->flush();

Since I have users who I know use Sophos, I would be really happy if this could be fixed ASAP. Thanks!