Max() Over (partition By ) Gives Error

I keep getting this error:

Msg 156, Level 15, State 1, Line 12
Incorrect syntax near the keyword 'over'.


What am I missing? The max() over statement looks just like the statement in the documentation.

select RegistrationId,
OrderId,
Sequence,
Title,
InformalFirstName,
FirstName,
MiddleName,
Lastname,
EntryDate,
max(Sequence) over(partition by RegistrationId) as 'maxsequence'
from registration
where OrderId = '68379449583' and
Year = '2008' and
Active = 'Yes'