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 ('41adaa6a5ed3e9e0f75313380122fb8a', -1, 1419298198, 1419298198, '36d3b52d', -1, 0, 0)

Line : 187
File : sessions.php