diff --git a/.travis.yml b/.travis.yml
index a915f7a46ec3d5..96f4997d380610 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -54,7 +54,9 @@ matrix:
         # Sphinx is pinned so that new versions that introduce new warnings won't suddenly cause build failures.
         # (Updating the version is fine as long as no warnings are raised by doing so.)
         # The theme used by the docs is stored separately, so we need to install that as well.
-        - python -m pip install sphinx==2.2.0 blurb python-docs-theme
+        #
+        # When updating Sphinx version, update also Doc/Makefile
+        - python -m pip install sphinx==3.2.1 blurb python-docs-theme
       script:
         - make check suspicious html SPHINXOPTS="-q -W -j4"
     - name: "Documentation tests"
diff --git a/Doc/Makefile b/Doc/Makefile
index c11a7ca5c1bcb7..3b54b8114c4b76 100644
--- a/Doc/Makefile
+++ b/Doc/Makefile
@@ -143,6 +143,7 @@ clean:
 venv:
 	$(PYTHON) -m venv $(VENVDIR)
 	$(VENVDIR)/bin/python3 -m pip install -U pip setuptools
+	# When updating Sphinx version, update also .travis.yml
 	$(VENVDIR)/bin/python3 -m pip install -U Sphinx==3.2.1 blurb python-docs-theme
 	@echo "The venv has been created in the $(VENVDIR) directory"