diff --git a/jest.config.ts b/jest.config.ts
index 61b4ecf..0b65960 100644
--- a/jest.config.ts
+++ b/jest.config.ts
@@ -11,6 +11,9 @@ const jestConfig: JestConfigWithTsJest = {
     "default",
     ["jest-junit", { outputDirectory: "test-results/jest" }],
   ],
+  moduleNameMapper: {
+    '^(\\.{1,2}/.*)\\.js$': '$1',
+  },
   coverageReporters: ["lcov", "text", "text-summary"],
   setupFiles: [],
   preset: "ts-jest/presets/default-esm",
diff --git a/lib/index.ts b/lib/index.ts
index 35270e7..c197f92 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;