Problems getting straight quotes (xelatex and tufte_handout)


I’m trying to convert R Markdown to PDF using the tufte_handout style and xelatex. My header-includes contains the fontspec package so that I can customise fonts. However, if I specify a custom monospaced font, all the quotes become curly and point in only one direction. I found this blog post:

and tried adding the upquote package to no avail, and apparently, Yihui has already fixed this issue too. I also messed around with Ligatures but it didn’t work. The only way I’ve managed to get straight quotes in code is to use the default Courier New; any other monospaced font (I tried Andale Mono, Menlo, inconsolata, Share Tech Mono, Operator Mono) reverts to curly quotes.

Has anyone experienced this issue and have ideas on how to resolve it? Thank you!