Avoiding empty page between a very full page and the index?

I'm getting an empty page between the last page of the book and the index. The reason seems to be an over-full last page of text. I'm already using openany.

In the following example, all the "bla" lines are on the first page, the second page is blank (erroneously), and the third page contains the index. Commenting one line of "bla" fixes the situation: the first page contains the lines of "bla" and the second page contains the index. Is there anything else I can do? (Is this a bug I should report?)

\documentclass[a4paper,openany,twoside,notitlepage]{tufte-book} \usepackage{makeidx} \makeindex \title{Test} \author{Alex Schroeder} \begin{document} \maketitle% this prints the handout title, author, and date \newthought{Test}\index{Test}. bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla \printindex \end{document}