Hide squid in the header

I have a squid server installed, and I'd like it to be hidden when looking into the headers.

First of all, I was getting both squid and the version on the headers:

curl -i ip_address

HTTP/1.0 400 Bad Request
Server: squid/3.1.10
Mime-Version: 1.0
Date: Wed, 04 Feb 2015 18:58:06 GMT
Content-Type: text/html
Content-Length: 3157
X-Squid-Error: ERR_INVALID_URL 0
Vary: Accept-Language
Content-Language: en
X-Cache: MISS from host.example.com
X-Cache-Lookup: NONE from host.example.com:80
Via: 1.0 host.example.com (squid/3.1.10)
Connection: close

I then set the following directive in /etc/squid/squid.conf:

httpd_suppress_version_string on

And now I'm not getting the squid version:

HTTP/1.0 400 Bad Request
Server: squid
Mime-Version: 1.0
Date: Wed, 04 Feb 2015 19:11:06 GMT
Content-Type: text/html
Content-Length: 13
X-Squid-Error: ERR_INVALID_URL 0
Vary: Accept-Language
Content-Language: en
X-Cache: MISS from host.example.com
X-Cache-Lookup: NONE from host.example.com:80
Via: 1.0 host.example.com (squid)
Connection: close

But I'd like to hide squid from the headers.

I get the same results when I try to use the machine as a proxy, f.i. by using:

curl -i -x http://user:password@ip_address:80 http://iplocation.net

I've tried the solutions form this question, but it's not working.

Any suggestions?

Thanks in advance.