diff --git a/doc/Makefile b/doc/Makefile
index 4bbc252fb6..6929f3dbe0 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -47,7 +47,7 @@ SPHINXEXTRA = -E -j $(shell $(PYTHON) -c 'import multiprocessing;print(multiproc
 # we only want to use explicitly listed files.
 DOXYFILES      = $(shell sed -n -e 's/\#.*$$//' -e '/^ *INPUT \+=/,/^[A-Z_]\+ \+=/p' doxygen/Doxyfile.in | sed -e 's/@LAMMPS_SOURCE_DIR@/..\/src/g' -e 's/\\//g' -e 's/ \+/ /' -e 's/[A-Z_]\+ \+= *\(YES\|NO\|\)//') 
 
-.PHONY: help clean-all clean clean-spelling epub mobi rst html pdf spelling anchor_check style_check char_check xmlgen fasthtml
+.PHONY: help clean-all clean clean-spelling epub mobi html pdf spelling anchor_check style_check char_check xmlgen fasthtml
 
 # ------------------------------------------
 
diff --git a/doc/utils/sphinx-config/conf.py.in b/doc/utils/sphinx-config/conf.py.in
index 722e678d17..c7cfe3edb3 100644
--- a/doc/utils/sphinx-config/conf.py.in
+++ b/doc/utils/sphinx-config/conf.py.in
@@ -38,7 +38,7 @@ sys.path.append(os.path.join(LAMMPS_DOC_DIR, 'src', '_ext'))
 # -- General configuration ------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
-#needs_sphinx = '1.0'
+needs_sphinx = '5.2.0'
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
@@ -53,10 +53,6 @@ extensions = [
     'tab_or_note',
     'breathe',
 ]
-# 2017-12-07: commented out, since this package is broken with Sphinx 16.x
-#             yet we can no longer use Sphinx 15.x, since that breaks with
-#             newer version of the multiprocessor module.
-#    'sphinxcontrib.images',
 
 images_config = {
   'default_image_width' : '25%',