diff --git a/INTERPRETING.md b/INTERPRETING.md
index 81cd00d55b..9f4f1eedfd 100644
--- a/INTERPRETING.md
+++ b/INTERPRETING.md
@@ -160,6 +160,11 @@ located at `test/language/import/nested/dep.js`.
 
 Files bearing a name ending in `.json` are intended to be interpreted as JSON.
 
+### Implementations without ECMA-402
+
+Tests in the `test/intl402/` folder assume that the implementation supports [ECMA-402, the ECMAScript Internationalization API Specification](https://tc39.github.io/ecma402/).
+When testing an implementation lacking the capabilities in ECMA-402, the tests in that folder should be skipped.
+
 ## Test Results
 
 By default, tests signal failure by generating an uncaught exception. If