Temperature conversion issue

[rufuswilson]

I was very surprised by the result of the following I was expecting 0.001.

>>> import pint
>>> pint.__version__
'0.23'
>>> UR = pint.UnitRegistry
>>> q = UR.Quantity(1.0,'millidegree_Celsius')
>>> q.m_as(units="degree_Celsius")
-273.149

Am I missing something or is this a bug?

[dalito]

This is known but not yet fixed, see #1754 (and #1381).