Oracle problem in a GROUP BY clause

One of our clients reported that the following query doesn't work on Oracle:

SELECT
FLOOR(qg.grade/$bandwidth) AS band,
COUNT(1) AS num
FROM
{$CFG->prefix}quiz_grades qg,
{$CFG->prefix}quiz q
WHERE qg.quiz = q.id AND qg.quiz = $quizid
".($useridlist?"AND qg.userid IN ($useridlist) ":'')."
GROUP BY band
ORDER BY band

From: mod/quiz/report/reportlib.php, quiz_report_grade_bands()

Repeating the FLOOR function in the GROUP BY clause seems to fix it though (see attached patch against 1.9).