QString::replace fails with QRegExp and QRegularExpression

QString str("/");
qDebug() << str.replace(QRegularExpression("/?$"), "/test");

This outputs /test/test. To reproduce, run the attached test program.

Python:

>>> print(re.sub('/?$', '/test', '/'));
/test

Sed:

$ echo "/" | sed 's#/?$#/test#'
/test