Filled box hides next boxes in same area

[Reinis]

###System info#######################
Python version 2.7.5
Installed according to instructions for Microsoft Windows here http://dev.laptop.org/pub/gasp/downloads/
OS: Windows7 Enterprise, Service Pack 1
GASP version: python-gasp-0.2.0beta1.win32
Pygame version: pygame-1.9.1.win32-py2.7

###Description#######################
The script added below is run through Windows command shell by reading a script file. Issue is that two boxes that represent left and right windows in a drawing of a house are not visible. I have added a picture with printscreens of results when:
- first box is filled - (Box((20, 20), 100, 100, True, color=color.BLUE)
- first box is not filled - Box((20, 20), 100, 100, False, color=color.BLUE)

###Script#######################
from gasp import * # import everything from the gasp library

begin_graphics() # open the graphics canvas

Box((20, 20), 100, 100, True, color=color.BLUE) # the house
Box((55, 20), 30, 50) # the door
Box((40, 80), 20, 20) # the left window
Box((80, 80), 20, 20) # the right window
Line((20, 120), (70, 160)) # the left roof
Line((70, 160), (120, 120)) # the right roof

update_when('key_pressed') # keep the canvas open until a key is pressed
end_graphics() # close the canvas (which would happen
                            # anyway, since the script ends here, but it
                            # is better to be explicit).