Winger has it dead right.
If you look at the wall behind the boy it's white. If you get an inexpensive "slave" flash and put it on a table, obscure it with a plant, lamp or some other thing. it should have the power to lighten the wall for you.
This happens with most hot shoe automatic flashes. The sensor reads the foreground(roughly central) subject and quenches the flash when that area receives enough light, if it didn't the foreground would wash out.