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 ('d8cbdec7c52daf114eb1e99ea19e20e2', -1, 1529334914, 1529334914, '36e05573', -4, 0, 0)

Line : 187
File : sessions.php