diff --git a/tox.ini b/tox.ini
index 66032eb27..ee536857a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@ setenv =
 deps = -r{toxinidir}/test-requirements.txt
 commands =
     /bin/rm -f .testrepository/times.dbm
-    python setup.py testr --slowest --testr-args='{posargs}'
+    python setup.py testr --slowest --testr-args='--concurrency 1 {posargs}'
     oslo-config-generator --config-file=etc/vitrage/vitrage-config-generator.conf
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY