# Setuptools 78.0.1 breaking package installation

{{< callout type="info" >}}
Update: Setuptools released [version 78.0.2 postponing this breaking change](https://setuptools.pypa.io/en/stable/history.html#bugfixes).
{{< /callout >}}

A recent update to setuptools ([version 78.0.1](https://setuptools.pypa.io/en/latest/history.html#deprecations-and-removals)) is breaking installations of many packages, particularly older or unmaintained ones that use dash-separated keys instead of the now-required underscore format.

Setuptools 78.0.1 introduced a breaking change that enforces strict naming conventions in `setup.cfg` files. Specifically:

- Options containing dashes (e.g., `description-file`) are no longer accepted
- Options must use underscore format instead (e.g., `description_file`)

The error looks like this:

```
setuptools.errors.InvalidConfigError: Invalid dash-separated key 'descriptionfile' in 'metadata' (setup.cfg), please use the underscore name 'description_file' instead.
```

While this validation has been in the code since 2021, it appears to have been fully enforced with the 78.0.1 release.

## Affected Packages

Many packages are affected, [including](https://github.com/pypa/setuptools/issues/4910) but not limited to:

- ansible-vault
- opentracing
- pysdf
- pypd
- pyspark (via dependencies)

## Current Solutions

As of now, there are several workarounds:

### 1. Downgrade setuptools

Some users report success by pinning setuptools to an earlier version:

```bash
pip install setuptools==77.0.3
```


### 2. For uv users

If you're using the uv package manager, create a file named "build.txt" with the line setuptools<=77.0.3 and run

- For `uv pip`: You can use build constraints
  ```bash
  uv pip install --build-constraint build.txt <package>
  ```

- For `uv sync`: Unfortunately, build constraints aren't currently supported with `uv sync`. The uv team is working on a fix—see [here](https://github.com/astral-sh/uv/issues/12434) and [here](https://github.com/astral-sh/uv/issues/12441).


## A Fix is Coming

The setuptools team is working on a fix. A pull request ([#4911](https://github.com/pypa/setuptools/pull/4911)) has been created to revert the removals introduced in v78.0.0, which should restore compatibility with packages using dash-separated keys.