diff --git a/run_tests.sh b/run_tests.sh
index bfa16c628b..b764f18fe9 100755
--- a/run_tests.sh
+++ b/run_tests.sh
@@ -23,7 +23,7 @@ function usage {
   echo "  --tools-path <dir>          Location of the tools directory"
   echo "                               Default: \$(pwd)"
   echo "  --concurrency <concurrency> How many processes to use when running the tests. A value of 0 autodetects concurrency from your CPU count"
-  echo "                               Default: 1"
+  echo "                               Default: 0"
   echo ""
   echo "Note: with no options specified, the script will try to run the tests in a virtual environment,"
   echo "      If no virtualenv is found, the script will ask if you would like to create one.  If you "
@@ -85,7 +85,7 @@ no_pep8=0
 coverage=0
 debug=0
 update=0
-concurrency=1
+concurrency=0
 
 LANG=en_US.UTF-8
 LANGUAGE=en_US:en
diff --git a/tox.ini b/tox.ini
index 3e4311f43a..c4eb23296d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,7 +10,7 @@ install_command = pip install --allow-all-external --allow-insecure netaddr -U {
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = python -m glance.openstack.common.lockutils python setup.py test --slowest \
-    --testr-args='--concurrency 1 {posargs}'
+    --testr-args='--concurrency 0 {posargs}'
 whitelist_externals = bash
 
 [tox:jenkins]