diff --git a/tox.ini b/tox.ini
index fedd04c..832a7b3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -34,7 +34,7 @@
 sitepackages = {[tempestenv]sitepackages}
 # 'all' includes slow tests
 setenv = {[tempestenv]setenv}
-         OS_TEST_TIMEOUT=1200
+         OS_TEST_TIMEOUT={env:OS_TEST_TIMEOUT:1200}
 deps = {[tempestenv]deps}
 commands =
   find . -type f -name "*.pyc" -delete
@@ -44,7 +44,7 @@
 sitepackages = True
 # 'all' includes slow tests
 setenv = {[tempestenv]setenv}
-         OS_TEST_TIMEOUT=1200
+         OS_TEST_TIMEOUT={env:OS_TEST_TIMEOUT:1200}
 deps = {[tempestenv]deps}
 commands =
   find . -type f -name "*.pyc" -delete