Pandas panel not adding column

gistfile1.py

import numpy as np
import pandas as ps

np.random.seed(0)

index=range(3)
columns = list('abc')

panel = ps.Panel.from_dict(
    {'A' : ps.DataFrame(np.random.randn(3, 3), index=index, columns=columns),
     'B' : ps.DataFrame(np.random.randn(3, 3), index=index, columns=columns),
     'C' : ps.DataFrame(np.random.randn(3, 3), index=index, columns=columns)
    }, orient='minor')

replace = ps.DataFrame(np.eye(4,4), index=range(4), columns=list('abcd'))

panel.loc[:,:,'A'] = replace

print(panel.loc[:, :, 'A']) #'d' column not added