phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('31e2c768b6c693ccb3a7989e890a06df', -1, 1417194301, 1417194301, '365cfd80', -1, 0, 0)

Line : 187
File : sessions.php