---
title: 'Invalid Custom Route `source`'
---

## Why This Error Occurred

A pattern could not be parsed when defining custom routes or a middleware `matcher`.

This could have been due to trying to use normal `RegExp` syntax like negative lookaheads (`?!exclude`) without following [`path-to-regexp`](https://github.com/pillarjs/path-to-regexp)'s syntax.

## Possible Ways to Fix It

Wrap the `RegExp` part of your `source` as an un-named parameter.

##### Custom Routes

**Before**

```js
{
  source: '/feedback/(?!general)',
  destination: '/feedback/general'
}
```

**After**

```js
{
  source: '/feedback/((?!general).*)',
  destination: '/feedback/general'
}
```

##### Middleware

**Before**

```ts filename="middleware.ts"
const config = {
  matcher: '/feedback/(?!general)',
}
```

**After**

```ts filename="middleware.ts"
const config = {
  matcher: '/feedback/((?!general).*)',
}
```

## Useful Links

- [path-to-regexp](https://github.com/pillarjs/path-to-regexp)
- [un-named parameters](https://github.com/pillarjs/path-to-regexp#unnamed-parameters)
