diff --git a/tox.ini b/tox.ini
index bb64ef710..21c949b22 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,20 +1,16 @@
 [tox]
-# TODO(yamahata): enable tests of py34.
-# Those unit tests are temporalily disabled until its stabilization
-#envlist = py27,py34,pep8
 envlist = docs,pep8,py27
 minversion = 1.6
 skipsdist = True
 
-# TODO(yamahata): re-enable unit tests again
-# disable unit tests for now until stabilization
 [testenv:py34]
 commands = bash -c "echo do nothing for py34 for now. enable after stablized"
 
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
 usedevelop = True
-install_command = pip install -U {opts} {packages}
+install_command =
+    pip install -U -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
        setuptools-git>=0.4
@@ -65,6 +61,8 @@ commands =
     python setup.py build_sphinx
 
 [testenv:releasenotes]
+# Note: remove once infra supports constraints for this target
+install_command = pip install -U --force-reinstall {opts} {packages}
 commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
@@ -83,6 +81,8 @@ commands =
   coverage html --include='tacker/*' -d covhtml -i
 
 [testenv:venv]
+# Note: remove once infra supports constraints for this target
+install_command = pip install -U --force-reinstall {opts} {packages}
 commands = {posargs}
 
 [flake8]