Using sqrt with units and .prefix() causes problems

[cream68]

I am using the following lambda function to apply sqrt to variables with units:

sqrt = lambda x: x.sqrt()

This works very well until I force the units using .prefix('something') on the variables used inside the sqrt function:

super(Physical, self).__setattr__("value", float(value))
                                               ^^^^^^^^^^^^
TypeError: float() argument must be a string or a real number, not 'complex'

Is there a way to circumvent this problem or a better approach to ensure sqrtworks with prefixed units?

Thank you for your help!