# Generating gradetables with parts using the exam class

I've just started using the exam class to typeset, well, an exam, and when using the \gradetable command to create the final grade table, it only shows me the points at the granularity of a question, but not the parts (or subparts, etc.) of that question, as the following example illustrates:

\documentclass[addpoints]{exam}

\begin{document}

\begin{questions}
\question
What if there were no air?
\begin{parts}
\part[4]
Describe the effect on the balloon industry.
\part[6]
Describe the effect on the aircraft industry.
\end{parts}
\question
\begin{parts}
\part[12]
Define the universe.
Give three examples.
\part[8]
If the universe were to end, how would you know?
\end{parts}
\end{questions}