Frame inner wall with sloped ceiling - risk of mold behind?

[plan-g]

In order to have a headboard, I need to build a vertical interior wall up to chest height against a slanted ceiling wall in the bedroom.

This will create an enclosed space facing an exterior wall.

Is there a risk of mold in the space (enclosed space and cold exterior wall)?
How can I avoid this?

 

[plan-g]

To be able to have a headboard, I will put up a vertical interior wall up to chest height against a slanted ceiling wall in the bedroom.

It will be a closed space that faces an exterior wall.

Is there a risk of mold in the space (enclosed space and cold exterior wall)?
How to avoid this?

In a previous house, I found extensive mold damage behind wardrobes that were placed against the interior side of an exterior wall. Hence the question.