diff --git a/doc/requirements.txt b/doc/requirements.txt
index d3ac8c4d520e9a9ffbb0469875aeaa1d6255e73c..0c9944e17487cf81ef010084366011ca92894d1d 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -7,5 +7,5 @@
 # be installed in a specific order.
 openstackdocstheme>=1.19.0 # Apache-2.0
 reno>=2.5.0 # Apache-2.0
-sphinx>=1.8.0,!=2.1.0;python_version>='3.4'  # BSD
+sphinx>=1.8.0,!=2.1.0 # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD
diff --git a/tox.ini b/tox.ini
index aab0805429230ff9365ff82273876c7396907bf1..328575904cdfeac4ab555b1393f1c2473253a16e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,8 @@
 [tox]
-minversion = 2.5.0
+minversion = 3.1
 skipsdist = True
 envlist = py37,pep8,pypy
+ignore_basepython_conflict = True
 
 [testenv]
 basepython = python3