404 error found in logs when purging nginx cache [#2185645]

I am running BOA 2.1.0 with Nginx. expire module and purge module enabled. I have noticed that anonymous users cannot see updated posts, so I had a better look at the log files. in /var/log/nginx/speed_purge.log I found, exactly for the time when a new comment was published:

"127.0.0.1" www.mydomain.com [30/Jan/2014:19:31:58 +0100] "GET /purge-normal/ttp://www.mydomain.com/ HTTP/1.1" 404 162 97 333 "-" "-" 0.000 "-"
"127.0.0.1"  www.mydomain.com [30/Jan/2014:19:31:58 +0100] "GET /purge-normal/ttp://</strong>www.mydomain.com/node/4042 HTTP/1.1" 404 162 106 333 "-" "-" 0.000 "-"

As you can see, there is a 404 error, upon the relevant purge.

Indeed, if I simulate the action with curl, it is the same result

# curl -X GET -H "Host:www.mydomain.com" "127.0.0.1:8888/purge-normal/ttp://www.mydomain.com/node/4042"                                        |
<html>
<head><title>404 Not Found</title></head>
<body bgcolor="white">
<center><h1>404 Not Found</h1></center>
<hr><center>nginx</center>
</body>
</html>

Whereas if I request directly the node, without including the full domain, it works

# curl -X GET -H "Host:www.mydomain.com" "127.0.0.1:8888/purge-normal/node/4042"                                                               
<html>
<head><title>Successful purge</title></head>
<body bgcolor="white">
<center><h1>Successful purge</h1>
<br>Key : normalwww.mydomain.comGET/node/4042
<br>Path: /var/lib/nginx/speed/d0/fb/c3/ed7be8a504561ddf25fca58486c3fbd0
</center>
<hr><center>nginx/1.5.6</center>
</body>
</html>

* Please note that there is not a full "http" on the beginning of the request, but just "ttp". Is this normal?
* I have no possibility to disable full domain for caches, since this setting is forced by BOA