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 ('8bd2bc66d52ef5cd32b066cc4dd433d5', -1, 1417163820, 1417163820, '36c43e17', 2, 0, 0)

Line : 187
File : sessions.php