A [bisect][1] shows that the error was introduced [here][4] ([2021-02-26][2]). [1]: src:/timeline?nc&bid=ya26b6597e3nacd63062eby5f8bf99579n99aab32da1y05dbea9b26y15795a96a8na631c38d22sde9c86c9e4y310dac342enccb8cf5256ne4d1970ef1 [4]: src:/vdiff?from=310dac342e7b1f9b&to=e4d1970ef17b2330&nc [2]: src:/timeline?n=20&c=e4d1970ef17b2330 Here is the cross-platform test case: > ~~~ CREATE TABLE onerow(x INT); INSERT INTO onerow(x) VALUES(0); SELECT * FROM ( SELECT null AS aaa FROM onerow UNION ALL SELECT 'missing' AS aaa FROM onerow ) AS a LEFT JOIN (SELECT 1 AS bbb) AS b ON a.aaa IS NULL; ~~~