diff --git a/lambda/cleaner.js b/lambda/cleaner.js
index 4c1d3c3..b99ce9b 100644
--- a/lambda/cleaner.js
+++ b/lambda/cleaner.js
@@ -1,5 +1,6 @@
 'use strict';
 
+const { ResourceNotFoundException } = require("@aws-sdk/client-lambda");
 const utils = require('./utils');
 
 /**
@@ -39,7 +40,7 @@ const cleanup = async(lambdaARN, alias) => {
         await utils.deleteLambdaAlias(lambdaARN, alias);
         await utils.deleteLambdaVersion(lambdaARN, FunctionVersion);
     } catch (error) {
-        if (error.code === 'ResourceNotFoundException') {
+        if (error instanceof ResourceNotFoundException) {
             console.error('OK, even if version/alias was not found');
             console.error(error);
         } else {
diff --git a/lambda/utils.js b/lambda/utils.js
index c708d6a..99046f7 100644
--- a/lambda/utils.js
+++ b/lambda/utils.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const { CreateAliasCommand, DeleteAliasCommand, DeleteFunctionCommand, GetAliasCommand, GetFunctionConfigurationCommand, InvokeCommand, LambdaClient, PublishVersionCommand, UpdateAliasCommand, UpdateFunctionConfigurationCommand, waitUntilFunctionActive, waitUntilFunctionUpdated } = require("@aws-sdk/client-lambda");
+const { CreateAliasCommand, DeleteAliasCommand, DeleteFunctionCommand, GetAliasCommand, GetFunctionConfigurationCommand, InvokeCommand, LambdaClient, PublishVersionCommand, UpdateAliasCommand, UpdateFunctionConfigurationCommand, waitUntilFunctionActive, waitUntilFunctionUpdated, ResourceNotFoundException } = require("@aws-sdk/client-lambda");
 const { GetObjectCommand, S3Client } = require("@aws-sdk/client-s3");
 const url = require('url');
 
@@ -56,7 +56,8 @@ module.exports.verifyAliasExistance = async(lambdaARN, alias) => {
         await utils.getLambdaAlias(lambdaARN, alias);
         return true;
     } catch (error) {
-        if (error.code === 'ResourceNotFoundException') {
+        console.log("Error during verifyAlias (probably OK!)")
+        if (error instanceof ResourceNotFoundException) {
             // OK, the alias isn't supposed to exist
             console.log('OK, even if missing alias ');
             return false;
diff --git a/test/unit/test-lambda.js b/test/unit/test-lambda.js
index 4dcc29a..28a13e3 100644
--- a/test/unit/test-lambda.js
+++ b/test/unit/test-lambda.js
@@ -4,7 +4,7 @@ const sinon = require('sinon');
 const expect = require('expect.js');
 
 var awsV3Mock = require('aws-sdk-client-mock');
-const { CreateAliasCommand, DeleteAliasCommand, DeleteFunctionCommand, GetAliasCommand, InvokeCommand, LambdaClient, PublishVersionCommand, UpdateAliasCommand, UpdateFunctionConfigurationCommand } = require("@aws-sdk/client-lambda");
+const { CreateAliasCommand, DeleteAliasCommand, DeleteFunctionCommand, GetAliasCommand, InvokeCommand, LambdaClient, PublishVersionCommand, UpdateAliasCommand, UpdateFunctionConfigurationCommand, ResourceNotFoundException } = require("@aws-sdk/client-lambda");
 
 const utils = require('../../lambda/utils');
 
@@ -103,8 +103,7 @@ describe('Lambda Functions', async() => {
             });
         getLambdaAliasStub = sandBox.stub(utils, 'getLambdaAlias')
             .callsFake(async() => {
-                const error = new Error('alias is not defined');
-                error.code = 'ResourceNotFoundException';
+                const error = new ResourceNotFoundException('alias is not defined');
                 throw error;
             });
         sandBox.stub(utils, 'getLambdaPower')
@@ -224,8 +223,7 @@ describe('Lambda Functions', async() => {
                     if (alias === 'RAM128') {
                         return { FunctionVersion: '1' };
                     } else {
-                        const error = new Error('alias is not defined');
-                        error.code = 'ResourceNotFoundException';
+                        const error = new ResourceNotFoundException('alias is not defined');
                         throw error;
                     }
                 });
@@ -262,7 +260,6 @@ describe('Lambda Functions', async() => {
             getLambdaAliasStub = sandBox.stub(utils, 'getLambdaAlias')
                 .callsFake(async() => {
                     const error = new Error('very bad error');
-                    error.code = 'VeryBadError';
                     throw error;
                 });
             await invokeForFailure(handler, { lambdaARN: 'arnOK', num: 5 });
@@ -322,8 +319,7 @@ describe('Lambda Functions', async() => {
             deleteLambdaVersionStub && deleteLambdaVersionStub.restore();
             deleteLambdaVersionStub = sandBox.stub(utils, 'deleteLambdaVersion')
                 .callsFake(async() => {
-                    const error = new Error('version is not defined');
-                    error.code = 'ResourceNotFoundException';
+                    const error = new ResourceNotFoundException('version is not defined');
                     throw error;
                 });
             await invokeForSuccess(handler, eventOK);
@@ -333,8 +329,7 @@ describe('Lambda Functions', async() => {
             deleteLambdaAliasStub && deleteLambdaAliasStub.restore();
             deleteLambdaAliasStub = sandBox.stub(utils, 'deleteLambdaAlias')
                 .callsFake(async() => {
-                    const error = new Error('alias is not defined');
-                    error.code = 'ResourceNotFoundException';
+                    const error = new ResourceNotFoundException('alias is not defined');
                     throw error;
                 });
             await invokeForSuccess(handler, eventOK);
@@ -345,7 +340,6 @@ describe('Lambda Functions', async() => {
             deleteLambdaVersionStub = sandBox.stub(utils, 'deleteLambdaVersion')
                 .callsFake(async() => {
                     const error = new Error('very bad error');
-                    error.code = 'VeryBadError';
                     throw error;
                 });
             await invokeForFailure(handler, eventOK);
@@ -1664,8 +1658,7 @@ describe('Lambda Functions', async() => {
             getLambdaAliasStub && getLambdaAliasStub.restore();
             getLambdaAliasStub = sandBox.stub(utils, 'getLambdaAlias')
                 .callsFake(async() => {
-                    const error = new Error('alias is not defined');
-                    error.code = 'ResourceNotFoundException';
+                    const error = new ResourceNotFoundException('alias is not defined');
                     throw error;
                 });
             setLambdaPowerStub && setLambdaPowerStub.restore();
diff --git a/test/unit/test-utils.js b/test/unit/test-utils.js
index 41204f9..fae37e7 100644
--- a/test/unit/test-utils.js
+++ b/test/unit/test-utils.js
@@ -5,7 +5,7 @@ const expect = require('expect.js');
 
 var awsV3Mock = require('aws-sdk-client-mock');
 const {
-    CreateAliasCommand, DeleteAliasCommand, DeleteFunctionCommand, GetAliasCommand, GetFunctionConfigurationCommand, InvokeCommand, LambdaClient, PublishVersionCommand, UpdateFunctionConfigurationCommand, UpdateAliasCommand } = require("@aws-sdk/client-lambda");
+    CreateAliasCommand, DeleteAliasCommand, DeleteFunctionCommand, GetAliasCommand, GetFunctionConfigurationCommand, InvokeCommand, LambdaClient, PublishVersionCommand, UpdateFunctionConfigurationCommand, UpdateAliasCommand, ResourceNotFoundException } = require("@aws-sdk/client-lambda");
 const { GetObjectCommand, S3Client } = require("@aws-sdk/client-s3");
 
 process.env.sfCosts = `{"us-gov-west-1": 0.00003,"eu-north-1": 0.000025,
@@ -139,8 +139,7 @@ describe('Lambda Utils', () => {
         it('should return false if the alias does not exists', async () => {
             sandBox.stub(utils, 'getLambdaAlias')
                 .callsFake(async () => {
-                    const error = new Error('alias is not defined');
-                    error.code = 'ResourceNotFoundException';
+                    const error = new ResourceNotFoundException('alias is not defined');
                     throw error;
                 });
             const aliasExists = await utils.verifyAliasExistance('arnOK', 'aliasName');