README.md in ruby-next-0.10.4 vs README.md in ruby-next-0.10.5

- old
+ new

@@ -474,9 +474,11 @@
 
 **NOTE:** Make sure you have `backports` gem installed globally or added to your bundle (if you're using `bundle exec ruby-next ...`).
 
 **NOTE:** For Ruby 2.2, safe navigation operator (`&.`) and squiggly heredocs (`<<~TXT`) support is provided.
 
+**IMPORTANT:** Unparser `~> 0.4.8` is required to run the transpiler on Ruby <2.4.
+
 ## Proposed and edge features
 
 Ruby Next aims to bring edge and proposed features to Ruby community before they (hopefully) reach an official Ruby release.
 This includes:
 