diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 4e3838a52ee2..26e937ff335b 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -110,10 +110,6 @@ You can run parts of the test case separately:
   ```sh
   npx run-s prepare test-promises
   ```
-- [ECMAScript `Observable` test case](https://github.com/tc39/proposal-observable):
-  ```sh
-  npx run-s prepare test-observables
-  ```
 - CommonJS entry points tests:
   ```sh
   npx run-s prepare test-entries