diff --git a/README.md b/README.md
index facdc94..1a87b51 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,8 @@
 Hello, World
 ============
 
+WARNING: This is the legacy py2 version. See the latest version in this repo's `main` branch.
+
 A simple program, and an example of how to structure a python project. Demonstrates a basic package
 file structure (using [flat layout]) and a way to define a [single package version] shared between
 package metadata and program runtime.