diff --git a/Makefile.python b/Makefile.python
--- a/Makefile.python
+++ b/Makefile.python
@@ -53,8 +53,9 @@
 	make -C docs
 
 .PHONY: distclean
-# clean up Python bytecode files. Also consider random *.pyc files, in case
-# Python 2.x has been run by mistake
+
+# Clean up Python bytecode files and a bunch of Python tool caches.
 distclean:
 	find . -type d -name __pycache__ | xargs rm -rf
 	find . -type f -name '*.pyc' -delete
+	rm -rf .tox/ .mypy_cache/