diff --git a/tox.ini b/tox.ini
index e2c5b31..ef1705a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -34,13 +34,11 @@ commands = isort {posargs:-rc -c} -sp setup.cfg merkle_tree_stream/ test/
 [testenv:format]
 description = format the source
 skipdist = True
-basepython = python3.6
 deps = black
 commands = black {posargs:--check} merkle_tree_stream/ test/
 
 [testenv:type]
 description = type check the source
-basepython = python3.7
 skipdist = True
 deps = mypy
 commands = mypy merkle_tree_stream/ test/