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 ('d7f8c1de9114aea07a6fd6ef06be50ea', -1, 1414260737, 1414260737, '36e2fc8e', 42, 0, 0)

Line : 187
File : sessions.php