Flask-SQLAlchemy specified key too long

Question

I have the following Flask-SQLAlchemy schema:

class User(db.Model, UserMixin):
    __tablename__ = "users"

    id = db.Column(db.Integer, primary_key=True)

    username = db.Column(db.String(64), nullable=False, unique=True)
    password = db.Column(db.String(255), nullable=False, server_default="")

    email = db.Column(db.String(254), nullable=False, unique=True)
    confirmed_at = db.Column(db.DateTime())

    is_enabled = db.Column(db.Boolean(), nullable=False, default=False)

    def is_active(self):
        return self.is_enabled

Which generates the SQL (I'm using MySQL):

CREATE TABLE users (
    id INTEGER NOT NULL AUTO_INCREMENT, 
    username VARCHAR(64) NOT NULL, 
    password VARCHAR(255) NOT NULL DEFAULT '', 
    email VARCHAR(254) NOT NULL, 
    confirmed_at DATETIME, 
    is_enabled BOOL NOT NULL, 
    PRIMARY KEY (id), 
    UNIQUE (username), 
    UNIQUE (email), 
    CHECK (is_enabled IN (0, 1))
)

However, this gives me the error "Specified key was too long; max key length is 767 bytes".

Note that this is not a duplicate of Can't create_all Flask-SQLAlchemy - specified key was too long; that question suggested shortening unique column lengths to <255 characters, and I have tried that with no success.

I would like, if possible, to keep the email field at 254 characters as that is the max length as defined by the spec.