diff --git a/tox.ini b/tox.ini
index 5427f0f..ee0c5dd 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,6 +17,9 @@ deps =
     -rnearley-requirements.txt
     -rregex-requirements.txt
 
+# For regex testing
+extras = regex
+
 # to always force recreation and avoid unexpected side effects
 recreate=True