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 ('1bd978ec989d20da82db4e7c7eac72d3', -1, 1410997092, 1410997092, '36591560', 42, 0)

Line : 158
File : sessions.php