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 ('5a6ce15005a1e73e279a078ee3aa8c25', -1, 1397632466, 1397632466, '6ca2d4d7', 44, 0, 0)

Line : 187
File : sessions.php