diff --git a/src/errors/UnauthorizedError.ts b/src/errors/UnauthorizedError.ts
index 64550e5a..f4f0bc96 100644
--- a/src/errors/UnauthorizedError.ts
+++ b/src/errors/UnauthorizedError.ts
@@ -13,6 +13,7 @@ export class UnauthorizedError extends Error {
 
   constructor(code: ErrorCode, error: ErrorLike) {
     super(error.message);
+    Object.setPrototypeOf(this, UnauthorizedError.prototype);
     this.code = code;
     this.status = 401;
     this.name = 'UnauthorizedError';
diff --git a/test/UnauthorizedError.test.ts b/test/UnauthorizedError.test.ts
new file mode 100644
index 00000000..d6952131
--- /dev/null
+++ b/test/UnauthorizedError.test.ts
@@ -0,0 +1,19 @@
+import { UnauthorizedError } from '../src/errors/UnauthorizedError';
+import assert from 'assert';
+
+describe('Unauthorized Error', () => {
+  const e = new UnauthorizedError('credentials_bad_format', new Error('a'));
+
+  it('should be an instance of UnauthorizedError', () => {
+    assert.ok(e instanceof UnauthorizedError);
+  });
+
+  it('should contains the error code', () => {
+    assert.ok(e.code, 'credentials_bad_format');
+  });
+
+  it('should contains the error message', () => {
+    assert.ok(e.code, 'a');
+  });
+});
+