leaf_node() method of a Function object not acting correctly

I'm encountering an error when trying to adapt the highest node of a hierarchical function object. I can adapt the function space and the mesh (and also the problem object which is not demonstrated below) using the .leaf_node() method but the function object is giving me problems. If I use u.child() instead of u.leaf_node() then it works, but then it has to be updated after the third adaptation.

Thanks
Mike

Demo code:
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from dolfin import *

mesh = UnitSquare(2,2)

V = FunctionSpace(mesh, "Lagrange", 1) # Order 1 function space
u = Function(V)

print mesh.depth(), V.depth(), u.depth()

print mesh == mesh.leaf_node()
print mesh.leaf_node(), V.leaf_node(), u.leaf_node()
adapt(mesh) # Adapt mesh, new mesh assigned to bottom
adapt(V, mesh.leaf_node()) #Adapt V based on refined mesh
adapt(u,mesh.leaf_node()) #Adapt u based on refined mesh
print mesh.depth(), V.depth(), u.depth()

adapt(mesh.leaf_node()) #Adapt refined mesh, new mesh added to bottom
adapt(V.leaf_node(),mesh.leaf_node()) #Adapt V's leaf node based on newly refined mesh
adapt(u.leaf_node(),mesh.leaf_node()) #Adapt u's leaf node based on newly refined mesh ***FAIL***
#adapt(u.child(),mesh.leaf_node()) #Adapt u's first child, coincident with supposed leaf node **Works**

print mesh.depth(), V.depth(), u.depth()
~~~~~~~