Actress Sandra Bullock is sporting a bump on her forehead after accidentally running into a wall during a trip to Disneyland.

The Speed star recently joined her The Heat co-stars Melissa MCCarthy and comedian Michael MCDonald for a family day out at the California theme park, but she was left disoriented after enjoying a ride on the Space Mountain rollercoaster and smacked her head against a concrete wall.

The incident has left her with a small injury to the right side of her temple - and she's convinced the mishap is the result of bad karma.

She explains, "We went to Disneyland, Melissa MCCarthy and I, we took the kids, we took a couple friends of ours... Michael MCDonald, who's in our film... He's very funny but he's just mean and it's just towards me that he's mean, so I decided I'm going to be mean back... but everytime I did it, something horrible would happen to me. Like, I fell over the railing once...

"All I remember (about the accident) is that I turned my head and there was this blinding light and there's a crack in my head. Allegedly my knees buckled and I just, I ran into a wall. It was because I was being mean back (to MCDonald). I guess it's a karma thing... I still have a lump."