itersize not honored when using named cursor with RealDictCursor

Consider the following program with the default implementation of RealDictCursor:

import psycopg2.extras
conn = psycopg2.connect('dbname=test', connection_factory=psycopg2.extras.RealDictConnection)
curs = conn.cursor('unique_name')
curs.itersize = 2000
curs.execute("select * from foo limit 25")
curs.fetchone()

The output with PSYCOPG_DEBUG=1 contains the following lines:

[0x7f603d53c700]     FETCH FORWARD 1 FROM "unique_name"

I have to override the Cursor class like this to fetch the proper number of rows:

class Cursor(psycopg2.extras.RealDictCursor):
    def next(self):
        return psycopg2.extras._cursor.next(self)

class Connection(psycopg2.extras._connection):
    """A connection that uses `Cursor` automatically."""
    def cursor(self, name=None):
        if name is None:
            return psycopg2.extras._connection.cursor(self, cursor_factory=Cursor)
        else:
            return psycopg2.extras._connection.cursor(self, name, cursor_factory=Cursor)

conn = psycopg2.connect('dbname=test', connection_factory=Connection)
...

The debug output is OK:

[0x7f86ba488700]     FETCH FORWARD 2000 FROM "unique_name"