phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('8ceb06d5ebfeaa1b7fdbd142db8b66ab', -1, 1417245747, 1417245747, '365159b6', -9, 0, 0)

Line : 187
File : sessions.php