MissingMethodException: Method not found: 'System.Xml.XmlReaderSettings.set_MaxCharactersFromEntities' with Matrix

I use Matrix from http://www.ag-software.net for XMPP. AG-Software team said that I should use AG-Software » Download directory

But it doesn’t work. I have error:

MissingMethodException: Method not found: 'System.Xml.XmlReaderSettings.set_MaxCharactersFromEntities'.
System.Xml.Linq.XDocument.Parse (System.String text, LoadOptions options)
System.Xml.Linq.XDocument.Parse (System.String text)
Matrix.Crypt.ElGamal.ElGamal.FromXmlString (System.String p_string)
Matrix.License.License.Validate ()
Matrix.License.LicenseManager.SetLicense (System.String lic)

They recommended to ask unity team about it:

The new Unity IL2CPP compiler has many
bugs, the last we checked it wasn’t
able to compile MatriX properly to cpp
code. So if you are using the IL2CPP
compiler I ask you to contact Unity
directly for support.

Hi, there is in my github Working Library of XMPP implementation.