diff --git a/tox.ini b/tox.ini
index e575b4f..9f52f0d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -28,7 +28,9 @@
 
 [testenv:all]
 sitepackages = {[tempestenv]sitepackages}
+# 'all' includes slow tests
 setenv = {[tempestenv]setenv}
+         OS_TEST_TIMEOUT=1200
 deps = {[tempestenv]deps}
 commands =
   bash tools/pretty_tox.sh '{posargs}'