[Reg 5.15 -> 6.1.0] QVector print result after growth is invalid

#include <QDebug>
#include <QVector>

int main(int, char **) {
  QVector<qint64> v;
  for (int i = 0; i < 7; ++i) {
    v.append(i);
    qDebug() << i << v.at(i);
  }
  qDebug() << v;
  return 0;
}

0 0
1 1
2 2
3 3
4 4
5 5
6 6
QList(0, 1, 2, 3, 4, 5, 6)

0 0
1 1
2 2
3 3
4 4
5 5
6 6
QList(0, 1, 2, 3, 4, -930837747982139387, 6)

...
QList(0, 1, 2, 3, 4, 61361544922923013, 6)

...
QList(0, 1, 2, 3, 4, 79657418409115653, 6)