diff --git a/TODO.md b/TODO.md
index d68fe61..ae47327 100644
--- a/TODO.md
+++ b/TODO.md
@@ -10,6 +10,7 @@ Roadmap for fixes and features.
  - Unit tests
  - Plural unit names
  - Releases
+ - Unit substitutions
 
 ## General
  - CLI Options: version, help, evaluate