diff --git a/tox.ini b/tox.ini
index 4420324..8fe8833 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,25 +1,28 @@
 [tox]
 envlist=flake8
 
+[testenv]
+basepython = python3
+
 [testenv:sphinx]
 deps =
   django < 2
   .[testing]
   pifpaf
 commands =
   {envpython} -m pifpaf run postgresql -- make -C docs html
 
 [testenv:sphinx-dev]
 deps =
   django < 2
-  -r requirements-swh-dev.txt
+  -rrequirements-swh-dev.txt
   pifpaf
 commands =
   {envpython} -m pifpaf run postgresql -- make -C docs html
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8