diff --git a/tox.ini b/tox.ini
index d5e3980..e75f3e2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -21,10 +21,12 @@ deps =
 basepython = python2.7
 
 [testenv:pep8]
+basepython = python3
 commands = flake8
 skip_install = True
 
 [testenv:cover]
+basepython = python3
 setenv =
     {[testenv]setenv}
     PYTHON=coverage run --source shade --parallel-mode
@@ -35,9 +37,11 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
+basepython = python3
 commands = python setup.py build_sphinx
 
 [testenv:venv]
+basepython = python3
 usedevelop = true
 commands = {posargs}