MariaDB 5.5 or MySQL: executemany() doesn't work with NULL values

import mariadb

conn=mariadb.connect(user="georg", database="test")

cursor=conn.cursor()

cursor.execute("CREATE TEMPORARY TABLE ind1 (a int, b int default 2,c int)")

vals = [(1,4,3),(None, 2, 3)]

cursor.executemany("INSERT INTO ind1 VALUES (?,?,?)", vals)

cursor.execute("SELECT a, b, c FROM ind1")

row= cursor.fetchall()

print(row)