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) VALUES ('79718d37c5217fef4004d9e5c714ea8a', -1, 1414024553, 1414024553, '36a1bffe', 10, 0)

Line : 315
File : sessions.php