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 ('5515edb2c40a91f1865d0ec387e09b14', -1, 1490328767, 1490328767, 'ac44417d', 14, 0)

Line : 158
File : sessions.php