phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'phpbb_sessions.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 ('7f2904e18cf0757b474ed95660a74ecd', -1, 1768184920, 1768184920, 'd849d897', 12, 0, 0)

Line : 187
File : sessions.php