diff --git a/puppet/zulip_internal/files/nagios_plugins/check_postgres_backup b/puppet/zulip_internal/files/nagios_plugins/check_postgres_backup
index f44750561f..655b83155d 100755
--- a/puppet/zulip_internal/files/nagios_plugins/check_postgres_backup
+++ b/puppet/zulip_internal/files/nagios_plugins/check_postgres_backup
@@ -16,7 +16,7 @@ def report(state, msg):
     print "%s: %s" % (state, msg)
     exit(states[state])
 
-if subprocess.check_output(['psql', '-t', '-c',
+if subprocess.check_output(['psql', 'postgres', '-t', '-c',
                             'SELECT pg_is_in_recovery()']).strip() != 'f':
     report('OK', 'this is not the primary')