diff --git a/src/observables/ScalarObservable.ts b/src/observables/ScalarObservable.ts
index 20c4fdc89c..b591af8f46 100644
--- a/src/observables/ScalarObservable.ts
+++ b/src/observables/ScalarObservable.ts
@@ -85,4 +85,8 @@ export default class ScalarObservable<T> extends Observable<T> {
       return new ScalarObservable(result);
     }
   }
+
+  scan<R>(project: (acc: R, x: T) => R, acc?: R): Observable<R> {
+    return this.reduce(project, acc);
+  }
 }