diff --git a/doc/requirements.txt b/doc/requirements.txt
index 1d9bc5a6..3c906b82 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,6 +1,5 @@
 # This is required for the docs build jobs
-sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7' # BSD
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2;python_version>='3.4' # BSD
+sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
 openstackdocstheme>=1.20.0 # Apache-2.0
 
 # This is required for the releasenotes build jobs
diff --git a/tox.ini b/tox.ini
index 99999cca..5099a0d3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,12 +1,13 @@
 [tox]
-minversion = 2.0
+minversion = 3.1
 skipsdist = True
 envlist = releasenotes
+ignore_basepython_conflict = True
 
 [testenv]
+basepython = python3
 install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master} {opts} {packages}
 
 [testenv:releasenotes]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html