diff --git a/tox.ini b/tox.ini
index fefc11ca5..6e573ed68 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,6 +8,7 @@ envlist = py34,py34-integration,misc,pep257,pyflakes,pep8,mccabe,pylint,pyroma,c
 
 [testenv]
 # https://bitbucket.org/hpk42/tox/issue/246/ - only needed for Windows though
+basepython = python3
 setenv =
     QT_QPA_PLATFORM_PLUGIN_PATH={envdir}/Lib/site-packages/PyQt5/plugins/platforms
     PYTEST_QT_API=pyqt5
@@ -31,6 +32,7 @@ commands =
     {envpython} scripts/dev/check_coverage.py {posargs}
 
 [testenv:py34-integration]
+basepython = python3
 setenv = {[testenv]setenv}
 passenv = {[testenv]passenv}
 deps = {[testenv]deps}