Work Phone field - Format

I am using the demographic Phone field on a Registration web form. The Customers from Germany are having problem entering thier phone number. For Ex when the customer enters this phone# +49 68 418091682 , its giving an error message asking the users to enter in one of the formats +49 XX XXXXXXXX. Howvever I was able to create a contact with that phone# without any issues. I am thinking that the validation checks behind the webform allows maximum length of 12 and so blocking this 13 digit number. Please advise

Thanks in advance.