I did a pgbouncer configuration using the following ini file: [databases] * = host=localhost port=5433 auth_user=pgbouncer [users] [pgbouncer] logfile = /pgdata/pcl_l002/pgbouncer/pgbouncer_pcl_l002.log pidfile = /pgdata/pcl_l002/pgbouncer/pgbouncer_pcl_l002.pid listen_addr = * listen_port = 6433 auth_type = hba auth_file = /pgdata/pcl_l002/pgbouncer/userlist_pcl_l002.txt auth_hba_file = /pgdata/pcl_l002/pg_hba.conf auth_user = pgbouncer auth_query = SELECT * FROM pgbouncer.get_auth($1) admin_users = monitor stats_users = stats, monitor max_client_conn = 500 default_pool_size = 20 log_connections = 1 log_disconnections = 1 log_pooler_errors = 1 Everything is fine as long as I connect to any database within the postgres cluster as any user. As soon as I try to connect to the pgbouncer admin console I get the following error: $ psql -h localhost -p 6433 -U monitor pgbouncer psql: server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request. $ psql -h localhost -p 6433 -U stats pgbouncer psql: server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request. There is always the same error within the pgbouncer logfile: ... ... 2021-12-07 16:56:53.550 CET [73046] LOG process up: PgBouncer 1.16.1, libevent 2.0.21-stable (epoll), adns: libc-2.17, tls: OpenSSL 1.0.2k-fips 26 Jan 2017 2021-12-07 16:57:00.969 CET [73046] FATAL @src/objects.c:312 in function put_in_order(): put_in_order: found existing elem $ pgbouncer --version PgBouncer 1.16.1 libevent 2.0.21-stable adns: libc-2.17 tls: OpenSSL 1.0.2k-fips 26 Jan 2017 Any idea? Thanks, Markus