phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry 'b4acf4f5f8561dd668d1609d6b9930f4' for key 'phpbb_sessions.PRIMARY'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('b4acf4f5f8561dd668d1609d6b9930f4', -1, 1770453555, 1770453555, 'd849d88f', -4, 0, 0)

Line : 187
File : sessions.php