diff --git a/packages/babel-plugin-transform-es2015-constants/README.md b/packages/babel-plugin-transform-es2015-constants/README.md
index f3e5376c17..5f9299972a 100644
--- a/packages/babel-plugin-transform-es2015-constants/README.md
+++ b/packages/babel-plugin-transform-es2015-constants/README.md
@@ -33,3 +33,7 @@ require("babel-core").transform("code", {
   plugins: ["transform-es2015-constants"]
 });
 ```
+
+## Note
+
+This transform on its own will compile `const` to `let`. If you need it to compile down to `var` then you must also install and enable [`transform-es2015-block-scoping`](../babel-plugin-transform-es2015-block-scoped-functions).