diff --git a/jest.config.ts b/jest.config.ts
index 61b4ecf..081468e 100644
--- a/jest.config.ts
+++ b/jest.config.ts
@@ -1,25 +1,18 @@
 import { type JestConfigWithTsJest } from "ts-jest";
 
 const jestConfig: JestConfigWithTsJest = {
-  rootDir: "./",
-  moduleFileExtensions: ["ts", "js"],
+  preset: "ts-jest/presets/default-esm",
+  moduleNameMapper: {
+    "^(\\.{1,2}/.*)\\.js$": "$1",
+  },
   testMatch: ["**/test/**/*.test.ts", "**/test/tests.ts"],
   coverageProvider: "v8",
   coveragePathIgnorePatterns: ["/node_modules/", "./test"],
-  extensionsToTreatAsEsm: [".ts"],
   reporters: [
     "default",
     ["jest-junit", { outputDirectory: "test-results/jest" }],
   ],
   coverageReporters: ["lcov", "text", "text-summary"],
-  setupFiles: [],
-  preset: "ts-jest/presets/default-esm",
-  transform: {
-    "^.+\\.ts?$": [
-      "ts-jest",
-      { useESM: true, tsconfig: "./tsconfig.test.json" },
-    ],
-  },
 };
 
 export default jestConfig;
diff --git a/lib/index.ts b/lib/index.ts
index cec7b2c..a8b7880 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -1,4 +1,4 @@
-import { base64UrlDecode } from "./base64-url-decode";
+import { base64UrlDecode } from "./base64-url-decode.js";
 
 export interface JwtDecodeOptions {
   header?: boolean;
diff --git a/lib/index.umd.ts b/lib/index.umd.ts
index ebc82f2..989b2da 100644
--- a/lib/index.umd.ts
+++ b/lib/index.umd.ts
@@ -1 +1 @@
-export { jwtDecode as default } from "./index";
+export { jwtDecode as default } from "./index.js";
diff --git a/rollup.config.ts b/rollup.config.ts
index 86778d4..b45b0bb 100644
--- a/rollup.config.ts
+++ b/rollup.config.ts
@@ -5,10 +5,7 @@ import livereload from "rollup-plugin-livereload";
 import serve from "rollup-plugin-serve";
 
 const isProduction = process.env.NODE_ENV === "production";
-const tsPlugin = typescript({
-  rootDir: "lib",
-  sourceMap: true,
-});
+const tsPlugin = typescript({ tsconfig: "tsconfig.build.json" });
 
 const plugins = [
   tsPlugin,
diff --git a/test/tests.ts b/test/tests.ts
index 8bb60c8..cc2d232 100644
--- a/test/tests.ts
+++ b/test/tests.ts
@@ -1,4 +1,4 @@
-import { jwtDecode, InvalidTokenError, JwtPayload } from "./../lib/index";
+import { jwtDecode, InvalidTokenError, JwtPayload } from "./../lib/index.js";
 import { describe, expect, it } from "@jest/globals";
 
 const token =
diff --git a/tsconfig.build.json b/tsconfig.build.json
new file mode 100644
index 0000000..5fdd1ea
--- /dev/null
+++ b/tsconfig.build.json
@@ -0,0 +1,8 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "target": "ES2017",
+    "rootDir": "./lib",
+    "sourceMap": true
+  }
+}
diff --git a/tsconfig.json b/tsconfig.json
index 1ce82b3..99bfead 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,15 +1,9 @@
 {
   "compilerOptions": {
-    "target": "ES2017",
-    "allowSyntheticDefaultImports": true,
-    "esModuleInterop": true,
-    "sourceMap": false,
-    "moduleResolution": "node",
-    "noImplicitAny": true,
-    "downlevelIteration": true,
-    "noImplicitThis": true,
+    "target": "ESNext",
+    "module": "ESNext",
+    "moduleResolution": "Node",
     "strict": true,
     "noEmitOnError": true
-  },
-  "exclude": ["./test", "./build/typings"]
+  }
 }
diff --git a/tsconfig.test.json b/tsconfig.test.json
deleted file mode 100644
index 744a3f3..0000000
--- a/tsconfig.test.json
+++ /dev/null
@@ -1,13 +0,0 @@
-{
-  "extends": "./tsconfig.json",
-  "compilerOptions": {
-    "noImplicitAny": false,
-    "target": "es6",
-    "noImplicitThis": false,
-    "alwaysStrict": false,
-    "strictBindCallApply": false,
-    "strictNullChecks": false,
-    "strictFunctionTypes": false,
-    "strictPropertyInitialization": false
-  }
-}