diff --git a/src/express/middleware.ts b/src/express/middleware.ts
index f528d96..8f2bbe3 100644
--- a/src/express/middleware.ts
+++ b/src/express/middleware.ts
@@ -1,12 +1,12 @@
 import debug from 'debug';
 import { NextFunction, Request, Response, RequestHandler } from 'express';
 import { Profile } from 'pprof-format';
-import { Profiler } from '../profilers/profiler';
-import { PyroscopeProfiler } from '../profilers/pyroscope-profiler';
-import { WallProfilerStartArgs } from '../profilers/wall-profiler';
-import { getProfiler } from '../utils/pyroscope-profiler';
+import { Profiler } from '../profilers/profiler.js';
+import { PyroscopeProfiler } from '../profilers/pyroscope-profiler.js';
+import { WallProfilerStartArgs } from '../profilers/wall-profiler.js';
+import { getProfiler } from '../utils/pyroscope-profiler.js';
 import { encode } from '@datadog/pprof';
-import { HeapProfilerStartArgs } from '../profilers/heap-profiler';
+import { HeapProfilerStartArgs } from '../profilers/heap-profiler.js';
 
 const log = debug('pyroscope');
 
diff --git a/src/index.ts b/src/index.ts
index e7a073c..243d74a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,19 +1,19 @@
-import 'regenerator-runtime/runtime';
+import 'regenerator-runtime/runtime.js';
 
-import expressMiddleware from './express/middleware';
-import { PyroscopeProfiler } from './profilers/pyroscope-profiler';
+import expressMiddleware from './express/middleware.js';
+import { PyroscopeProfiler } from './profilers/pyroscope-profiler.js';
 import {
   PyroscopeConfig,
   PyroscopeHeapConfig,
   PyroscopeWallConfig,
-} from './pyroscope-config';
-import { checkPyroscopeConfig } from './utils/check-pyroscope-config';
-import { getProfiler, setProfiler } from './utils/pyroscope-profiler';
-import { processConfig } from './utils/process-config';
-import { getEnv } from './utils/get-env';
+} from './pyroscope-config.js';
+import { checkPyroscopeConfig } from './utils/check-pyroscope-config.js';
+import { getProfiler, setProfiler } from './utils/pyroscope-profiler.js';
+import { processConfig } from './utils/process-config.js';
+import { getEnv } from './utils/get-env.js';
 import { setLogger as datadogSetLogger } from '@datadog/pprof';
-import { setLogger as ourSetLogger, Logger } from './logger';
-import { SourceMapper } from './sourcemapper';
+import { setLogger as ourSetLogger, Logger } from './logger.js';
+import { SourceMapper } from './sourcemapper.js';
 
 export function init(config: PyroscopeConfig = {}): void {
   checkPyroscopeConfig(config);
diff --git a/src/profilers/continuous-profiler.ts b/src/profilers/continuous-profiler.ts
index ffa4b75..aed47fa 100644
--- a/src/profilers/continuous-profiler.ts
+++ b/src/profilers/continuous-profiler.ts
@@ -1,6 +1,6 @@
 import debug from 'debug';
-import { ProfileExport, ProfileExporter } from '../profile-exporter';
-import { Profiler } from './profiler';
+import { ProfileExport, ProfileExporter } from '../profile-exporter.js';
+import { Profiler } from './profiler.js';
 
 const log = debug('pyroscope::profiler');
 
diff --git a/src/profilers/heap-profiler.ts b/src/profilers/heap-profiler.ts
index 8db66d2..03ef1fa 100644
--- a/src/profilers/heap-profiler.ts
+++ b/src/profilers/heap-profiler.ts
@@ -1,8 +1,8 @@
 import { heap, SourceMapper } from '@datadog/pprof';
 import { Profile } from 'pprof-format';
 
-import { ProfileExport } from '../profile-exporter';
-import { Profiler } from './profiler';
+import { ProfileExport } from '../profile-exporter.js';
+import { Profiler } from './profiler.js';
 import debug from 'debug';
 
 const log = debug('pyroscope::profiler::heap');
diff --git a/src/profilers/profiler.ts b/src/profilers/profiler.ts
index a4fbefd..4c57e2f 100644
--- a/src/profilers/profiler.ts
+++ b/src/profilers/profiler.ts
@@ -1,4 +1,4 @@
-import { ProfileExport } from '../profile-exporter';
+import { ProfileExport } from '../profile-exporter.js';
 
 export interface Profiler<TStartArgs> {
   getLabels(): Record<string, number | string>;
diff --git a/src/profilers/pyroscope-profiler.ts b/src/profilers/pyroscope-profiler.ts
index 3520d8b..fa952b0 100644
--- a/src/profilers/pyroscope-profiler.ts
+++ b/src/profilers/pyroscope-profiler.ts
@@ -1,8 +1,8 @@
-import { PyroscopeApiExporter } from '../pyroscope-api-exporter';
-import { ContinuousProfiler } from './continuous-profiler';
-import { WallProfiler, WallProfilerStartArgs } from './wall-profiler';
-import { HeapProfiler, HeapProfilerStartArgs } from './heap-profiler';
-import { PyroscopeConfig } from '../pyroscope-config';
+import { PyroscopeApiExporter } from '../pyroscope-api-exporter.js';
+import { ContinuousProfiler } from './continuous-profiler.js';
+import { WallProfiler, WallProfilerStartArgs } from './wall-profiler.js';
+import { HeapProfiler, HeapProfilerStartArgs } from './heap-profiler.js';
+import { PyroscopeConfig } from '../pyroscope-config.js';
 
 const MICROS_PER_SECOND = 1e6;
 const MS_PER_SECOND = 1e3;
diff --git a/src/profilers/wall-profiler.ts b/src/profilers/wall-profiler.ts
index 445739d..fe09695 100644
--- a/src/profilers/wall-profiler.ts
+++ b/src/profilers/wall-profiler.ts
@@ -1,8 +1,8 @@
 import { time, SourceMapper, LabelSet, TimeProfileNode } from '@datadog/pprof';
 import { Profile } from 'pprof-format';
 
-import { ProfileExport } from '../profile-exporter';
-import { Profiler } from './profiler';
+import { ProfileExport } from '../profile-exporter.js';
+import { Profiler } from './profiler.js';
 import debug from 'debug';
 
 const MICROS_PER_SECOND = 1e6;
diff --git a/src/pyroscope-api-exporter.ts b/src/pyroscope-api-exporter.ts
index cb0b90e..c9efd3a 100644
--- a/src/pyroscope-api-exporter.ts
+++ b/src/pyroscope-api-exporter.ts
@@ -4,11 +4,11 @@ import { encode } from '@datadog/pprof';
 import axios, { AxiosBasicCredentials, AxiosError } from 'axios';
 import FormData, { Headers } from 'form-data';
 import { Profile } from 'pprof-format';
-import { ProfileExport, ProfileExporter } from './profile-exporter';
-import { dateToUnixTimestamp } from './utils/date-to-unix-timestamp';
-import { processProfile } from './utils/process-profile';
+import { ProfileExport, ProfileExporter } from './profile-exporter.js';
+import { dateToUnixTimestamp } from './utils/date-to-unix-timestamp.js';
+import { processProfile } from './utils/process-profile.js';
 import debug from 'debug';
-import { PyroscopeConfig } from './pyroscope-config';
+import { PyroscopeConfig } from './pyroscope-config.js';
 
 const log = debug('pyroscope');
 
diff --git a/src/sourcemapper.ts b/src/sourcemapper.ts
index 3356eb2..c6296b8 100644
--- a/src/sourcemapper.ts
+++ b/src/sourcemapper.ts
@@ -23,7 +23,7 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import * as sourceMap from 'source-map';
-import { logger } from './logger';
+import { logger } from './logger.js';
 import pLimit from 'p-limit';
 
 const readFile = fs.promises.readFile;
diff --git a/src/utils/check-pyroscope-config.ts b/src/utils/check-pyroscope-config.ts
index dc4fe7a..7945f5c 100644
--- a/src/utils/check-pyroscope-config.ts
+++ b/src/utils/check-pyroscope-config.ts
@@ -2,7 +2,7 @@ import {
   PyroscopeConfig,
   PyroscopeHeapConfig,
   PyroscopeWallConfig,
-} from '../pyroscope-config';
+} from '../pyroscope-config.js';
 
 export function checkPyroscopeConfig(
   config: unknown
diff --git a/src/utils/get-env.ts b/src/utils/get-env.ts
index 8326a0c..7764932 100644
--- a/src/utils/get-env.ts
+++ b/src/utils/get-env.ts
@@ -1,4 +1,4 @@
-import { Environment } from '../environment';
+import { Environment } from '../environment.js';
 
 export function getEnv(): Environment {
   return {
diff --git a/src/utils/process-config.ts b/src/utils/process-config.ts
index 476d89f..4fff26f 100644
--- a/src/utils/process-config.ts
+++ b/src/utils/process-config.ts
@@ -1,5 +1,5 @@
-import { Environment } from '../environment';
-import { PyroscopeConfig } from '../pyroscope-config';
+import { Environment } from '../environment.js';
+import { PyroscopeConfig } from '../pyroscope-config.js';
 
 export function processConfig(
   config: PyroscopeConfig,
diff --git a/src/utils/pyroscope-profiler.ts b/src/utils/pyroscope-profiler.ts
index 2c5471f..82bc19d 100644
--- a/src/utils/pyroscope-profiler.ts
+++ b/src/utils/pyroscope-profiler.ts
@@ -1,4 +1,4 @@
-import { PyroscopeProfiler } from '../profilers/pyroscope-profiler';
+import { PyroscopeProfiler } from '../profilers/pyroscope-profiler.js';
 
 let pyroscopeProfiler: PyroscopeProfiler | undefined;
 
diff --git a/test/index.test.ts b/test/index.test.ts
index 23e08ed..c3bed60 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -2,8 +2,8 @@ import { describe, it, expect } from 'vitest';
 
 import fs from 'node:fs';
 import { Profile } from 'pprof-format';
-import Pyroscope from '../src';
-import { processProfile } from '../src/utils/process-profile';
+import Pyroscope from '../src/index.ts';
+import { processProfile } from '../src/utils/process-profile.ts';
 
 describe('typescript env', () => {
   it('has correct imports', () => {
diff --git a/test/middleware.test.ts b/test/middleware.test.ts
index b1043f5..98efe04 100644
--- a/test/middleware.test.ts
+++ b/test/middleware.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect } from 'vitest';
 
-import Pyroscope from '../src';
+import Pyroscope from '../src/index.js';
 import request from 'supertest';
 import express from 'express';
 
diff --git a/test/profiler.test.ts b/test/profiler.test.ts
index 113ea46..0327de5 100644
--- a/test/profiler.test.ts
+++ b/test/profiler.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect } from 'vitest';
 
-import Pyroscope from '../src';
+import Pyroscope from '../src/index.js';
 import express from 'express';
 import busboy from 'busboy';
 import { Profile } from 'pprof-format';