I don't know what changed to cause this (could be something in Debian, could be something in the kernel). On August 16th, I generated a 'make htmldocs' that looks fine. Yesterday, I generated one and it's missing these two crucial lines (there are many other changes, but restoring these two lines to any given file makes it look fine): <link rel="stylesheet" href="../_static/css/theme.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> I can't find any commits that look relevant. I have sphinx 4.3.1-1 installed. I also tried with 4.2.0-5 with the same result.