diff --git a/packages/core/router/router-response-controller.ts b/packages/core/router/router-response-controller.ts
index 008eea5a85d..4128e7fcab5 100644
--- a/packages/core/router/router-response-controller.ts
+++ b/packages/core/router/router-response-controller.ts
@@ -5,9 +5,9 @@ import {
   RequestMethod,
   MessageEvent,
 } from '@nestjs/common';
-import { isFunction, isObject } from '@nestjs/common/utils/shared.utils';
+import { isObject } from '@nestjs/common/utils/shared.utils';
 import { IncomingMessage } from 'http';
-import { EMPTY, lastValueFrom, Observable } from 'rxjs';
+import { EMPTY, lastValueFrom, Observable, isObservable } from 'rxjs';
 import { catchError, debounce, map } from 'rxjs/operators';
 import {
   AdditionalHeaders,
@@ -64,7 +64,7 @@ export class RouterResponseController {
   }
 
   public async transformToResult(resultOrDeferred: any) {
-    if (resultOrDeferred && isFunction(resultOrDeferred.subscribe)) {
+    if (isObservable(resultOrDeferred)) {
       return lastValueFrom(resultOrDeferred);
     }
     return resultOrDeferred;
@@ -152,8 +152,8 @@ export class RouterResponseController {
     });
   }
 
-  private assertObservable(result: any) {
-    if (!isFunction(result.subscribe)) {
+  private assertObservable(value: any) {
+    if (!isObservable(value)) {
       throw new ReferenceError(
         'You must return an Observable stream to use Server-Sent Events (SSE).',
       );
diff --git a/packages/websockets/web-sockets-controller.ts b/packages/websockets/web-sockets-controller.ts
index 75e790c8277..d01811e179b 100644
--- a/packages/websockets/web-sockets-controller.ts
+++ b/packages/websockets/web-sockets-controller.ts
@@ -1,9 +1,14 @@
 import { Type } from '@nestjs/common/interfaces/type.interface';
 import { Logger } from '@nestjs/common/services/logger.service';
-import { isFunction } from '@nestjs/common/utils/shared.utils';
 import { ApplicationConfig } from '@nestjs/core/application-config';
 import { MetadataScanner } from '@nestjs/core/metadata-scanner';
-import { from as fromPromise, Observable, of, Subject } from 'rxjs';
+import {
+  from as fromPromise,
+  Observable,
+  isObservable,
+  of,
+  Subject,
+} from 'rxjs';
 import { distinctUntilChanged, mergeAll } from 'rxjs/operators';
 import { GATEWAY_OPTIONS, PORT_METADATA } from './constants';
 import { WsContextCreator } from './context/ws-context-creator';
@@ -158,7 +163,7 @@ export class WebSocketsController {
     deferredResult: Promise<any>,
   ): Promise<Observable<any>> {
     const result = await deferredResult;
-    if (result && isFunction(result.subscribe)) {
+    if (isObservable(result)) {
       return result;
     }
     if (result instanceof Promise) {