Incorrect appearance of stacked density plot in polar coordinates

[ASmirnov-HORIS]

Example:

data = {
    'x': [1, 1, 1, 2],
    'g': ['a', 'a', 'b', 'b']
}
ggplot(data) + \
    geom_density(aes(x='x', fill='g'), position='stack') + \
    coord_polar()

Output:

Expected: