diff --git a/doc/requirements.txt b/doc/requirements.txt
index 9227414ca..1e4e69eb5 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -4,5 +4,5 @@
 
 openstackdocstheme>=1.19.0 # Apache-2.0
 reno!=2.3.1,>=1.8.0 # 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 b90a48436..3d7cfb974 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,8 @@
 [tox]
-minversion = 2.0
+minversion = 3.1
 envlist = py3,pep8
 skipsdist = True
+ignore_basepython_conflict = True
 
 [testenv]
 basepython = python3