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 ('8fe98745a6ec52d5d01a93be69db350c', -1, 1768185773, 1768185773, 'd849d897', 10, 0, 0)

Line : 187
File : sessions.php