> 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/0203-to-0227/aur0224.md).

# AUR0224

## Error Message

`AUR0224: Invalid @observable decorator usage, cannot determine property name`

## Description

This error occurs when Aurelia cannot determine the property name for an `@observable` decorator usage. This is usually caused by applying `@observable` in an unsupported way or in an environment that does not provide the required decorator metadata.

## Common Scenarios

* Using `@observable` without proper TypeScript decorator configuration.
* Applying `@observable` to an unsupported target (for example not a class field/property in the expected form).

## Solution

* Ensure your project is configured for decorators as required by Aurelia.
* Apply `@observable` to a class field/property as supported by your build setup.

## Troubleshooting

* Verify your TypeScript/bundler configuration for decorators.
* Check that the decorator is applied to a class field and not a local variable or unsupported construct.


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