phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '9d439806c9acf171492a978222ad64e3' for key 'PRIMARY'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('9d439806c9acf171492a978222ad64e3', -1, 1416755821, 1416755821, '365914f6', 2, 0, 0)

Line : 187
File : sessions.php