diff --git a/src/client.ts b/src/client.ts
index ed9d3be..77339c4 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -4,13 +4,13 @@
  */
 
 import debugBuilder from 'debug';
-import EventEmitter from 'eventemitter3';
+import { EventEmitter } from 'eventemitter3';
 import * as _ from 'lodash';
-import { HttpClient } from './http';
-import { IHeaders, IHttpClient, IMTOMAttachments, IOptions, ISecurity, SoapMethod, SoapMethodAsync } from './types';
-import { assert, findPrefix } from './utils';
-import { WSDL } from './wsdl';
-import { IPort, OperationElement, ServiceElement } from './wsdl/elements';
+import { HttpClient } from './http.js';
+import { IHeaders, IHttpClient, IMTOMAttachments, IOptions, ISecurity, SoapMethod, SoapMethodAsync } from './types.js';
+import { assert, findPrefix } from './utils.js';
+import { WSDL } from './wsdl/index.js';
+import { IPort, OperationElement, ServiceElement } from './wsdl/elements.js';
 
 /**
  * Read a ReadableStream to string
diff --git a/src/http.ts b/src/http.ts
index 7335801..1184046 100644
--- a/src/http.ts
+++ b/src/http.ts
@@ -5,13 +5,13 @@
 
 import debugBuilder from 'debug';
 import MIMEType from 'whatwg-mimetype';
-import { IExOptions, IHeaders, IHttpClient, IOptions } from './types';
-import { parseMTOMResp } from './utils';
+import { IExOptions, IHeaders, IHttpClient, IOptions } from './types.js';
+import { parseMTOMResp } from './utils.js';
 
 const debug = debugBuilder('fetch-soap');
 
 // Use default import for bundler compatibility (named imports from JSON don't work in webpack/Next.js)
-import pkg from '../package.json';
+import pkg from '../package.json' with { type: 'json' };
 const version = pkg.version;
 
 const textEncoder = new TextEncoder();
diff --git a/src/security/BasicAuthSecurity.ts b/src/security/BasicAuthSecurity.ts
index 50d61a2..ce7eae0 100644
--- a/src/security/BasicAuthSecurity.ts
+++ b/src/security/BasicAuthSecurity.ts
@@ -1,6 +1,6 @@
 import * as _ from 'lodash';
-import { IHeaders, ISecurity } from '../types';
-import { stringToBase64 } from '../utils';
+import { IHeaders, ISecurity } from '../types.js';
+import { stringToBase64 } from '../utils.js';
 
 export class BasicAuthSecurity implements ISecurity {
   private _username: string;
diff --git a/src/security/BearerSecurity.ts b/src/security/BearerSecurity.ts
index 8a12dde..e6ec0ef 100644
--- a/src/security/BearerSecurity.ts
+++ b/src/security/BearerSecurity.ts
@@ -1,5 +1,5 @@
 import * as _ from 'lodash';
-import { IHeaders, ISecurity } from '../types';
+import { IHeaders, ISecurity } from '../types.js';
 
 export class BearerSecurity implements ISecurity {
   private defaults;
diff --git a/src/security/WSSecurity.ts b/src/security/WSSecurity.ts
index b10ac16..15d9665 100644
--- a/src/security/WSSecurity.ts
+++ b/src/security/WSSecurity.ts
@@ -1,5 +1,5 @@
-import { ISecurity } from '../types';
-import { generateNonce, passwordDigest, xmlEscape } from '../utils';
+import { ISecurity } from '../types.js';
+import { generateNonce, passwordDigest, xmlEscape } from '../utils.js';
 
 const validPasswordTypes = ['PasswordDigest', 'PasswordText'];
 
diff --git a/src/security/index.ts b/src/security/index.ts
index 1d6287e..744edc7 100644
--- a/src/security/index.ts
+++ b/src/security/index.ts
@@ -1,3 +1,3 @@
-export * from './BasicAuthSecurity';
-export * from './BearerSecurity';
-export * from './WSSecurity';
+export * from './BasicAuthSecurity.js';
+export * from './BearerSecurity.js';
+export * from './WSSecurity.js';
diff --git a/src/soap.ts b/src/soap.ts
index 519c16c..78d0946 100644
--- a/src/soap.ts
+++ b/src/soap.ts
@@ -3,19 +3,19 @@
  * MIT Licensed
  */
 
-import { Client } from './client';
-import * as _security from './security';
-import { IOptions, IWSDLCache } from './types';
-import { wsdlCacheSingleton } from './utils';
-import { open_wsdl, WSDL } from './wsdl';
+import { Client } from './client.js';
+import * as _security from './security/index.js';
+import { IOptions, IWSDLCache } from './types.js';
+import { wsdlCacheSingleton } from './utils.js';
+import { open_wsdl, WSDL } from './wsdl/index.js';
 
 export const security = _security;
-export { Client } from './client';
-export { HttpClient } from './http';
-export { BasicAuthSecurity, BearerSecurity, WSSecurity } from './security';
-export { passwordDigest } from './utils';
-export * from './types';
-export { WSDL } from './wsdl';
+export { Client } from './client.js';
+export { HttpClient } from './http.js';
+export { BasicAuthSecurity, BearerSecurity, WSSecurity } from './security/index.js';
+export { passwordDigest } from './utils.js';
+export * from './types.js';
+export { WSDL } from './wsdl/index.js';
 
 type WSDLCallback = (error: any, result?: WSDL) => any;
 
diff --git a/src/types.ts b/src/types.ts
index b96744d..b9ca7c7 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,5 +1,5 @@
-import { WSDL } from './wsdl';
-import type { IHttpResponse } from './http';
+import { WSDL } from './wsdl/index.js';
+import type { IHttpResponse } from './http.js';
 
 export interface IHeaders {
   [k: string]: any;
diff --git a/src/utils.ts b/src/utils.ts
index 51cc080..ba917f8 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,5 +1,5 @@
-import { IMTOMAttachments, IWSDLCache } from './types';
-import { WSDL } from './wsdl';
+import { IMTOMAttachments, IWSDLCache } from './types.js';
+import { WSDL } from './wsdl/index.js';
 
 /**
  * Simple assertion function (replaces Node.js assert module)
diff --git a/src/wsdl/elements.ts b/src/wsdl/elements.ts
index 06f3d23..9456415 100644
--- a/src/wsdl/elements.ts
+++ b/src/wsdl/elements.ts
@@ -1,7 +1,7 @@
 import debugBuilder from 'debug';
 import * as _ from 'lodash';
-import { IWsdlBaseOptions } from '../types';
-import { assert, splitQName, TNS_PREFIX } from '../utils';
+import { IWsdlBaseOptions } from '../types.js';
+import { assert, splitQName, TNS_PREFIX } from '../utils.js';
 
 const debug = debugBuilder('fetch-soap');
 
diff --git a/src/wsdl/index.ts b/src/wsdl/index.ts
index de8095c..cc5aff5 100644
--- a/src/wsdl/index.ts
+++ b/src/wsdl/index.ts
@@ -9,11 +9,11 @@ import debugBuilder from 'debug';
 import * as _ from 'lodash';
 import * as sax from 'sax';
 import stripBom from 'strip-bom';
-import { HttpClient } from '../http';
-import { NamespaceContext } from '../nscontext';
-import { IOptions } from '../types';
-import { assert, findPrefix, splitQName, TNS_PREFIX, xmlEscape } from '../utils';
-import * as elements from './elements';
+import { HttpClient } from '../http.js';
+import { NamespaceContext } from '../nscontext.js';
+import { IOptions } from '../types.js';
+import { assert, findPrefix, splitQName, TNS_PREFIX, xmlEscape } from '../utils.js';
+import * as elements from './elements.js';
 
 const debug = debugBuilder('fetch-soap');
 
diff --git a/tsconfig.json b/tsconfig.json
index 0932ebc..2974be4 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -2,8 +2,8 @@
   "compileOnSave": true,
   "compilerOptions": {
     "target": "ES2020",
-    "module": "ESNext",
-    "moduleResolution": "bundler",
+    "module": "nodenext",
+    "moduleResolution": "nodenext",
     "lib": ["ES2020", "DOM"],
     "outDir": "lib",
     "rootDir": "src",