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) VALUES ('04487270ab8f20041f5ddf3e4fd18c64', -1, 1414154600, 1414154600, '3651a6c7', 42, 0)

Line : 158
File : sessions.php