SoundEffect plays slower/faster after source is changed

With this code:
import QtQuick 2.0
import QtMultimedia 5.6

SoundEffect

{ id: sound }

// later in the code in some QML element:
onSomeEvent:

{ sound.source = pathToNewSound + ".wav" sound.play(); }

On first call of onSomeEvent the sound plays correctly. On another calls of onSomeEvent, the sound plays faster/slower (probably depending on whether the first/previous sound was longer/shorter than this one).