diff --git a/src/AsyncCssPlugin.spec.ts b/src/AsyncCssPlugin.spec.ts
index 99b4951..68614f4 100644
--- a/src/AsyncCssPlugin.spec.ts
+++ b/src/AsyncCssPlugin.spec.ts
@@ -4,8 +4,8 @@ import HtmlWebpackPlugin from "html-webpack-plugin";
 import { describe, expect, it } from "vitest";
 import type { Compilation, Compiler } from "webpack";
 
-import AsyncCssPlugin from "./AsyncCssPlugin.js";
-import type { MessageType } from "./Options.js";
+import AsyncCssPlugin from "./AsyncCssPlugin.ts";
+import type { MessageType } from "./Options.ts";
 
 const createFakeCompiler = () => {
     const result = {
diff --git a/src/AsyncCssPlugin.ts b/src/AsyncCssPlugin.ts
index 758c33b..f88aa82 100644
--- a/src/AsyncCssPlugin.ts
+++ b/src/AsyncCssPlugin.ts
@@ -3,7 +3,7 @@
 import HtmlWebpackPlugin from "html-webpack-plugin";
 import type { Compilation, Compiler } from "webpack";
 
-import type { MessageType, Options } from "./Options.js";
+import type { MessageType, Options } from "./Options.ts";
 
 class AsyncCssPlugin {
     public constructor(options?: Options) {
diff --git a/src/test/vue/vue.spec.ts b/src/test/vue/vue.spec.ts
index fa5fb0e..f73cf13 100644
--- a/src/test/vue/vue.spec.ts
+++ b/src/test/vue/vue.spec.ts
@@ -5,7 +5,7 @@ import Service from "@vue/cli-service";
 
 import { describe, expect, it } from "vitest";
 
-import { getLinkProperties } from "../getLinkProperties.js";
+import { getLinkProperties } from "../getLinkProperties.ts";
 
 describe("AsyncCssPlugin", () => {
     describe("vue", () => {
diff --git a/src/test/webpack/async.config.ts b/src/test/webpack/async.config.ts
index 58c2cd2..3fb6d96 100644
--- a/src/test/webpack/async.config.ts
+++ b/src/test/webpack/async.config.ts
@@ -3,7 +3,7 @@
 import HtmlWebpackPlugin from "html-webpack-plugin";
 import MiniCssExtractPlugin from "mini-css-extract-plugin";
 import type { Configuration } from "webpack";
-import AsyncCssPlugin from "../../AsyncCssPlugin.js";
+import AsyncCssPlugin from "../../AsyncCssPlugin.ts";
 
 // eslint-disable-next-line import/no-default-export
 export default {
diff --git a/src/test/webpack/webpack.spec.ts b/src/test/webpack/webpack.spec.ts
index a1e89d7..b77a2a8 100644
--- a/src/test/webpack/webpack.spec.ts
+++ b/src/test/webpack/webpack.spec.ts
@@ -7,10 +7,10 @@ import { describe, expect, it } from "vitest";
 import type { Configuration } from "webpack";
 import webpack from "webpack";
 
-import { getLinkProperties } from "../getLinkProperties.js";
+import { getLinkProperties } from "../getLinkProperties.ts";
 
-import asyncOptions from "./async.config.js";
-import standardOptions from "./standard.config.js";
+import asyncOptions from "./async.config.ts";
+import standardOptions from "./standard.config.ts";
 
 const checkWebpack = async (
     options: Configuration,