exec limited to 4000 characters?

trying to execute this script gives only the first select as a result

declare @sp nvarchar(max)
select @sp = concat(N'select 1 ', replicate('-', 5000), char(13) + char(10), N'select 2')
exec (@sp)

but when I lower hyphens to 1000, I get also the second select How can I overcome this limit?