diff --git a/todo/TODO.md b/todo/TODO.md
index 8a22841b2..c9ba02a9d 100644
--- a/todo/TODO.md
+++ b/todo/TODO.md
@@ -36,3 +36,4 @@
   - Haskell: [#3035](https://github.com/rizonesoft/Notepad3/issues/3035) - Lexilla has `LexHaskell.cxx`
   - Racket: [#3035](https://github.com/rizonesoft/Notepad3/issues/3035) - Could use Lisp/Scheme lexer
   - Verilog HDL: [#4108](https://github.com/rizonesoft/Notepad3/issues/4108) - Lexilla has `LexVerilog.cxx`
+  - JSON5: [#5411](https://github.com/rizonesoft/Notepad3/issues/5411) - Extend JSON lexer or add `.json5` extension