diff --git a/tox.ini b/tox.ini
index 9bee3dd..92a5562 100644
--- a/tox.ini
+++ b/tox.ini
@@ -62,7 +62,7 @@
 deps = {[tempestenv]deps}
 commands =
     find . -type f -name "*.pyc" -delete
-    tempest run --regex {posargs}
+    tempest run --regex {posargs:''}
 
 [testenv:all-plugin]
 # DEPRECATED
@@ -82,7 +82,7 @@
     echo "WARNING: The all-plugin env is deprecated and will be removed"
     echo "WARNING  Please use the 'all' environment for Tempest plugins."
     find . -type f -name "*.pyc" -delete
-    tempest run --regex {posargs}
+    tempest run --regex {posargs:''}
 
 [testenv:all-site-packages]
 sitepackages = True
@@ -93,7 +93,7 @@
 deps = {[tempestenv]deps}
 commands =
     find . -type f -name "*.pyc" -delete
-    tempest run --regex {posargs}
+    tempest run --regex {posargs:''}
 
 [testenv:full]
 envdir = .tox/tempest