Adding mailbox using powershell

For adding a mailbox running following command: 

New-Mailbox -Alias chris -Name "Chris Ashton" -FirstName Chris -LastName Ashton -DisplayName "Chris Ashton" -UserPrincipalName name@domain.org

getting error:

A positional parameter cannot be found that accepts argument '-userprincipalname'

+categoryinfo: invalid argument:<:>[new-mailbox],parameterbindingexception

+fullyqualifiederrorId: PositionlParameterNotFound,newmailbox

Thanks in advance