Unicode characters are not sorted properly

Steps to reproduce

Create a contact named "Mab"
Create a contact named "Máa"
Create a contact named "Mb"
Look at the contacts list
Expected behaviour

The order should be Máa, Mab, Mb (accentuated characters have the exact same "weight" as the non-accentuated character (i.e. "á" when considered for sorting, can be, for all practical purposes, be replaced with "a"). Android contacts app gets this right, for example.

Actual behaviour

The order is Mab, Mb, Máa

Server configuration

Operating system: Ubuntu 15.10

Web server: Apache

Database: MySQL

PHP version: 5.6.11+dfsg-1ubuntu3.1

ownCloud version: 9.0.1-1.1

Contacts version: 1.1.0.0

Updated from an older ownCloud or fresh install: Updated

Signing status (ownCloud 9.0 and above):

No errors have been found.

List of activated apps:

Enabled:
  - activity: 2.2.1
  - calendar: 1.1
  - comments: 0.2
  - contacts: 1.1.0.0
  - dav: 0.1.6
  - documents: 0.12.0
  - external: 1.2
  - federatedfilesharing: 0.1.0
  - federation: 0.0.4
  - files: 1.4.4
  - files_external: 0.5.2
  - files_pdfviewer: 0.8
  - files_sharing: 0.9.1
  - files_texteditor: 2.1
  - files_trashbin: 0.8.0
  - files_versions: 1.2.0
  - files_videoplayer: 0.9.8
  - firstrunwizard: 1.1
  - gallery: 14.5.0
  - mail: 0.4.1
  - notifications: 0.2.3
  - provisioning_api: 0.4.1
  - search_lucene: 0.6.0
  - sharelinks: 1.0.1
  - systemtags: 0.2
  - tasks: 0.9.0
  - templateeditor: 0.1
  - updatenotification: 0.1.0

The content of config/config.php:

{
    "system": {
        "defaultapp": "calendar",
        "instanceid": "REMOVED",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "datadirectory": "\/srv\/owncloud\/data",
        "dbtype": "mysql",
        "version": "9.0.1.3",
        "appstoreenabled": true,
        "apps_paths": [
            {
                "path": "\/var\/www\/owncloud\/apps",
                "url": "\/apps",
                "writable": true
            }
        ],
        "dbname": "REMOVED",
        "dbhost": "REMOVED",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "forcessl": true,
        "theme": "",
        "maintenance": false,
        "trusted_domains": [
            "cloud.llucax.com.ar"
        ],
        "mail_from_address": "luca",
        "mail_smtpmode": "php",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "llucax.com.ar",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "remember_login_cookie_lifetime": 1296000,
        "session_lifetime": 259200,
        "session_keepalive": true,
        "preview_max_scale_factor": 1,
        "enabledPreviewProviders": [
            "OC\\Preview\\Image",
            "OC\\Preview\\Illustrator",
            "OC\\Preview\\Postscript",
            "OC\\Preview\\Photoshop",
            "OC\\Preview\\TIFF"
        ],
        "forceSSLforSubdomains": true,
        "memcache.local": "\\OC\\Memcache\\APCu",
        "appstore.experimental.enabled": true,
        "loglevel": 2,
        "trashbin_retention_obligation": "auto",
        "updatechecker": false
    }
}

Are you using external storage, if yes which one: Yes, local

Are you using encryption: NO

Are you using an external user-backend, if yes which one: NO

Client configuration

Browser: FF

Operating system: Debian testing

CardDAV-clients:

Logs

Nothing relevant

owncloud / contacts