diff --git a/roles/run-tempest-26/tasks/main.yaml b/roles/run-tempest-26/tasks/main.yaml
index f846006..7423bfb 100644
--- a/roles/run-tempest-26/tasks/main.yaml
+++ b/roles/run-tempest-26/tasks/main.yaml
@@ -62,7 +62,9 @@
       when: blacklist_stat.stat.exists
 
 - name: Run Tempest
-  command: tox -e {{tox_envlist}} {{tox_extra_args}} -- {{tempest_test_regex|quote}} {{blacklist_option|default('')}} \
+  command: tox -e {{tox_envlist}} {{tox_extra_args}} -- \
+            {{tempest_test_regex|quote if (tempest_test_regex|length>0)|default(None, True)}} \
+            {{blacklist_option|default(None)}} \
             --concurrency={{tempest_concurrency|default(default_concurrency)}} \
             --black-regex={{tempest_black_regex|quote}}
   args: