> For the complete documentation index, see [llms.txt](https://docs.aurelia.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aurelia.io/developer-guides/error-messages/router/aur3403.md).

# AUR3403

## Error Message

`AUR3403: Invalid instruction type %s for "toUrlComponent" operation. If you are seeing this error, then it is probably because of an internal bug. Please report it.`

## Description

This error occurs when `toUrlComponent` is called with an instruction type that it does not support.

## Troubleshooting

* If you call `toUrlComponent` directly, ensure you pass a supported instruction type.
* If you do not call it directly, this likely indicates a router bug; please report it with a reproduction.


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