Unspected behavour in beamer: mathtools and sansmathfonts

Looking this MWE, we can notice that using mathtools package the blank space between the operator d and f is correct:

\documentclass{beamer}\usepackage{mathtools}\begin{document}\begin{equation}\frac{df}{dt}\end{equation}\end{document}

But if I use \usepackage{sansmathfonts} the blank space vanished and increase in dt.

\documentclass{beamer}\usepackage{sansmathfonts}\usepackage{mathtools}\begin{document}\begin{equation}\frac{df}{dt}\end{equation}\end{document}

Since I have to use mathtools and sansmathfonts, how can I set it up to get the correct spacing?