phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('6d380bb07f5e7c8e0b911f7a37bd6d84', -1, 1539812065, 1539812065, '36e0f72a', 5, 0, 0)

Line : 187
File : sessions.php