I'm noticing that Nginx's log module is "collapsing" empty log variables primarily when using a TAB (\t) as a delimiter in the access log.

For example, if I use the following:

log_format main '$server_name $msec $remote_addr $cookie_x $cookie_y $cookie_z $status';

And a request does not have any cookies set (so $cookie_x, $cookie_y, and $cookie_z would be empty), then I would get a log line like this:

myserver.com 1331049809.478 10.10.15.50 - 200

I was expecting:

myserver.com 1331049809.478 10.10.15.50 - - - 200

The same thing happens with the $http_referer (when not set by the UA) and $upstream_addr (when serving static files).

Here's a link to my access log configuration:
https://gist.github.com/1988173

I'm using Nginx v1.1.16.

Has anyone experienced this before?