diff --git a/packages/html_builder/README.md b/packages/html_builder/README.md
index 2315fd4..9d930a4 100644
--- a/packages/html_builder/README.md
+++ b/packages/html_builder/README.md
@@ -8,6 +8,10 @@
 
 This package builds HTML AST's and renders them to HTML. It can be used as an internal DSL, i.e. for a templating engine.
 
+## Requirements
+
+* Dart SDK: 2.12.x or later
+
 ## Installation
 
 In your `pubspec.yaml`: