diff --git a/manual/index.rst b/manual/index.rst
index 48a6c06..5daf41a 100644
--- a/manual/index.rst
+++ b/manual/index.rst
@@ -144,10 +144,11 @@ ghostscript.
 
 Pre-built documentation is distributed with qpdf, so you should
 generally not need to rebuild the documentation. In order to build the
-documentation from its docbook sources, you need the docbook XML style
-sheets (http://downloads.sourceforge.net/docbook/). To build the PDF
-version of the documentation, you need Apache fop
-(http://xml.apache.org/fop/) version 0.94 or higher.
+documentation from source, you need to install `sphinx
+<https://sphinx-doc.org>`__. To build the PDF version of the
+documentation, you need `pdflatex`, `latexmk`, and a fairly complete
+LaTeX installation. Detailed requirements can be found in the Sphinx
+documentation.
 
 .. _ref.building: