diff --git a/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm b/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm
index c451aea3ac9..609275e2c26 100644
--- a/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm
+++ b/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm
@@ -112,6 +112,16 @@ sub adjust_database_contents
 			'drop extension if exists test_ext7');
 	}
 
+	# we removed these test-support functions in v18
+	if ($old_version < 18)
+	{
+		_add_st($result, 'regression', 'drop function ttdummy()');
+		_add_st($result, 'regression', 'drop function set_ttdummy(integer)');
+		_add_st($result, 'regression', 'drop function autoinc()');
+		_add_st($result, 'regression', 'drop function check_foreign_key()');
+		_add_st($result, 'regression', 'drop function check_primary_key()');
+	}
+
 	# we removed this test-support function in v17
 	if ($old_version >= 15 && $old_version < 17)
 	{