diff --git a/doc/src/Build_manual.rst b/doc/src/Build_manual.rst
index d86ad85827..e9a55134da 100644
--- a/doc/src/Build_manual.rst
+++ b/doc/src/Build_manual.rst
@@ -52,11 +52,11 @@ can be translated to different output format using the `Sphinx
 incorporates programmer documentation extracted from the LAMMPS C++
 sources through the `Doxygen <https://doxygen.nl/>`_ program.  Currently
 the translation to HTML, PDF (via LaTeX), ePUB (for many e-book readers)
-and MOBI (for Amazon Kindle readers) are supported.  For that to work a
-Python 3 interpreter, the ``doxygen`` tools and internet access to
-download additional files and tools are required.  This download is
-usually only required once or after the documentation folder is returned
-to a pristine state with ``make clean-all``.
+and MOBI (for Amazon Kindle(tm) readers) are supported.  For that to work a
+Python interpreter version 3.8 or later, the ``doxygen`` tools and
+internet access to download additional files and tools are required.
+This download is usually only required once or after the documentation
+folder is returned to a pristine state with ``make clean-all``.
 
 For the documentation build a python virtual environment is set up in
 the folder ``doc/docenv`` and various python packages are installed into