MacDonald made his Baggies debut against Plymouth in January

The 22-year-old joined the Baggies from the Dutch Second Division outfit during the January 2007 transfer window.

The Holland Under-21 international has not yet started a first-team game for Albion, but made 12 appearances from the bench last season.

"We've all seen glimpses of what Sherjill can produce," manager Tony Mowbray told his club's website.

"I see it regularly in training. Sherjill has undoubted quality and is gradually adapting to the English culture."

A minor knee operation in April limited the Dutchman's opportunities towards the end of the season.