Serpent: Redundant btyecode

[srya-b]

I created these two contracts as examples.
root.se

extern child.se: [double:[int256]:int256]

c = create('child.se')
c1 = create('child.se')
c2 = create('child.se')

def call():
    return(c.double(3))

and child.se

def double(x):
    return(x**2)

When root.se is compiled, redundant bytecode of the child.se is pasted into it instead of just once. Why is that?