Graph-Tool edge gradient in self loops

Question

So I'm currently encountering a problem where I try to give a self-looping edge a color gradient.

This however does not seem to work as intended. Is this bug?

Minimal example:

G = Graph(directed=False)
vlist = G.add_vertex(2) 
G.add_edge(0,0)
G.add_edge(0,1)

gradient = G.new_edge_property("vector<double>")
G.ep.gradient = gradient


G.ep.gradient[G.edge(0,0)]=[0,0,0,1,1,
                            0.5,1,1,1,1,
                            1,1,0,0,1]

G.ep.gradient[G.edge(0,1)]=[0,0,0,1,1,
                            0.5,1,1,1,1,
                            1,1,0,0,1]

graph_draw(G,pos=G.vp.pos,edge_gradient=G.ep.gradient,edge_control_points=G.ep.cp)

Edge from 0 to 1 does show the the gradient while edge from 0 to 0 does not.

Any ideas?

Thanks in advance!