phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('c6fbc5b208aab3698c940f32d27542a3', -1, 1529322428, 1529322428, '36c69e18', 14, 0, 0)

Line : 187
File : sessions.php