alignat: incorrect space before the equal sign [was: possible bug in alignat]

Created by: jason-s

$$\begin{alignat}{2}
a &= \frac{1}{2}b+c+d &=& e        \\
f &= \frac{2}{3}g+h   &=& i+j+k
\end{alignat}$$ 

in https://cdn.mathjax.org/mathjax/latest/test/sample-dynamic-2.html renders like this:

Note the small space before the e and i.