Why skimage mean filter does not work on float array?

I am going to apply a mean filter on an array of float with window_size=3 for example. I have found this library:

from skimage.filters.rank import mean
import numpy as np

x=np.array([[1,8,10],
           [5,2,9],
           [7,2,9],
           [4,7,10],
           [6,14,10]])

print(x)
print(mean(x, square(3)))


[[ 1  8 10]
 [ 5  2  9]
 [ 7  2  9]
 [ 4  7 10]
 [ 6 14 10]]
[[ 4  5  7]
 [ 4  5  6]
 [ 4  6  6]
 [ 6  7  8]
 [ 7  8 10]]

but this function can't run on float arrays:

from skimage.filters.rank import mean
import numpy as np

x=np.array([[1,8,10],
           [5,2,9],
           [7,2,9],
           [4,7,10],
           [6,14,10]])

print(x)
print(mean(x.astype(float), square(3)))

File "/home/pd/RSEnv/lib/python3.5/site-packages/skimage/util/dtype.py", line 236, in convert
raise ValueError("Images of type float must be between -1 and 1.")
    ValueError: Images of type float must be between -1 and 1.

How to solve this?