diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index bc39abd23e..2f381e556e 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -12,6 +12,8 @@ $node->init();
 $node->append_conf(
 	'postgresql.conf', qq(
 logging_collector = on
+# these ensure stability of test results:
+log_rotation_age = 0
 lc_messages = 'C'
 ));