iPhone 5s rattling Sleep/Wake button

I know that this problem is all over the internet, but I'd love to hear some comments from this community.

Yesterday I bought a space grey iPhone 5s 64GB from the Apple Store and today I noticed that the Sleep/Wake button rattles when you shake the iPhone horizontally. We're not talking audiophile-level soft rattling here: I can hear it easily from several meters.

Although this is a nuisance most of the time, it becomes a real problem when you start recording audio or video. (Who wants to hear a rattling button when playing back a recording?) To make matters worse, the microphone is distanced no more than a centimetre from the Sleep/Wake button.

I've recorded a voice memo so you can check it out for yourself. Note that I'm exploiting the problem by shaking my iPhone, but at least it gives you a good idea of how loud the rattling sound is.

Do any of you experience this problem? Is this normal, i.e. part of the design, or is this a manufacturing problem? Would I be able to exchange my iPhone?

I'd love to hear it!