fwrite() being screwy

[eluser]nZac[/eluser]
Heres an iteresting one for you, here is the code:

Code:

$msg = 'TEST';
$fp = fopen('./logs/somefile.php','ab');

flock($fp, LOCK_EX);    
fwrite($fp, $msg);
flock($fp, LOCK_UN);
fclose($fp);

within the file the output is this:

TESTTEST

I did a little research and found this is a known bug. Anyone know how to get past it?