1 files changed, 4 insertions, 0 deletions
diff --git a/tox.ini b/tox.ini
index 184e9365..c65f8f8b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -50,6 +50,10 @@ commands =
 [testenv:py39]
 basepython = python3.9
 
+[testenv:tip]
+# For running against the tip of master of CPython.
+basepython = /usr/local/cpython/bin/python3.9
+
 [testenv:doc]
 # Build the docs so we know if they are successful.  We build twice: once with
 # -q to get all warnings, and once with -QW to get a success/fail status