failing insert from select when sequence present

from sqlalchemy import *

m = MetaData()

t1 = Table(
    't', m,
    Column('id', Integer, Sequence('id_seq'), primary_key=True),
    Column('data', String)
)

t2 = Table(
    't2', m,
    Column('id', Integer),
    Column('data', String)
)

stmt = t1.insert().from_select(('data', ), select([t1.c.data]))

from sqlalchemy.dialects import postgresql
print stmt.compile(dialect=postgresql.dialect())

#!

sqlalchemy.exc.InvalidRequestError: This Sequence cannot be used directly as a column expression.  Use func.next_value(sequence) to produce a 'next value' function that's usable as a column element.

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