SQLite compiles false() incorrectly (in server_default)

import sqlalchemy
from sqlalchemy import schema
from sqlalchemy import types
from sqlalchemy.sql.expression import false
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

metadata = schema.MetaData()
BaseObject = declarative_base(metadata=metadata)

class Article(BaseObject):
    __tablename__ = "article"

    id = schema.Column(types.Integer(), primary_key=True)
    seen = schema.Column(types.Boolean(),
            server_default=false(), nullable=False)

engine = sqlalchemy.create_engine('sqlite:///:memory:')
metadata.create_all(engine)
Session = sessionmaker(bind=engine)

session = Session()
session.add(Article())
session.flush()

gives this error:

sqlalchemy.exc.IntegrityError: (IntegrityError) constraint failed u'INSERT INTO article DEFAULT VALUES' ()

the generated SQL gives a hint what is happening:

CREATE TABLE article (
    id INTEGER NOT NULL, 
    seen BOOLEAN DEFAULT false NOT NULL, 
    PRIMARY KEY (id), 
    CHECK (seen IN (0, 1))
)

It looks like {{{false()}}} is compiled to {{{false}}}, while the CHECK condition only accepts 0 and 1 as values.

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