diff --git a/src/whatsapp/repository/auth.repository.ts b/src/whatsapp/repository/auth.repository.ts
index 47fc579e..7aa1a427 100644
--- a/src/whatsapp/repository/auth.repository.ts
+++ b/src/whatsapp/repository/auth.repository.ts
@@ -5,7 +5,6 @@ import { Auth, ConfigService } from '../../config/env.config';
 import { Logger } from '../../config/logger.config';
 import { AUTH_DIR } from '../../config/path.config';
 import { IInsert, Repository } from '../abstract/abstract.repository';
-import { InstanceDto } from '../dto/instance.dto';
 import { AuthRaw, IAuthModel } from '../models';
 
 export class AuthRepository extends Repository {
@@ -65,7 +64,7 @@ export class AuthRepository extends Repository {
     }
   }
 
-  public async findInstanceNameById(instanceId: string): Promise<string> {
+  public async findInstanceNameById(instanceId: string): Promise<string | null> {
     try {
       this.logger.verbose('finding auth by instanceId');
       if (this.dbSettings.ENABLED) {
@@ -77,7 +76,7 @@ export class AuthRepository extends Repository {
 
       this.logger.verbose('finding auth in store is not supported');
     } catch (error) {
-      return '';
+      return null;
     }
   }
 }
diff --git a/src/whatsapp/services/monitor.service.ts b/src/whatsapp/services/monitor.service.ts
index 78c83c85..b449f693 100644
--- a/src/whatsapp/services/monitor.service.ts
+++ b/src/whatsapp/services/monitor.service.ts
@@ -162,6 +162,10 @@ export class WAMonitoringService {
   public async instanceInfoById(instanceId?: string) {
     this.logger.verbose('get instance info');
     const instanceName = await this.repository.auth.findInstanceNameById(instanceId);
+    if (!instanceName) {
+      throw new NotFoundException(`Instance "${instanceId}" not found`);
+    }
+
     if (instanceName && !this.waInstances[instanceName]) {
       throw new NotFoundException(`Instance "${instanceName}" not found`);
     }