phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO r2ok_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('2d9a30ac14d94ff6fdd8056fcffb49b0', -1, 1524206435, 1524206435, '3650082c', 31, 0, 0)

Line : 187
File : sessions.php