I can't see anything else in the bg that would make the shadows so it must be from the pillars in the wall. Looks a bit long for it to be correct. [ external image ]
I agree with Stephan however, the lack of smooth shadows does make it look wrong. At that distance you wouldn't get such sharp and defined outlines in the shadows as light would bleed around the pillar.
Not saying it's a bug but it still doesn't look right due to this.