diff --git a/src/internal/Observable.ts b/src/internal/Observable.ts
index 874d7e8092..0b467b27ae 100644
--- a/src/internal/Observable.ts
+++ b/src/internal/Observable.ts
@@ -17,7 +17,7 @@ import { config } from './config';
  */
 export class Observable<T> implements Subscribable<T> {
 
-  /** @internal */
+  /** Internal implementation detail, do not use directly. */
   public _isScalar: boolean = false;
 
   protected source: Observable<any>;