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 ('41d39f5d6d92d644150066767e08001a', -1, 1409701161, 1409701161, '3210a9dc', -1, 0, 0)

Line : 187
File : sessions.php