dependabot: Error : .github#L1 No event triggers defined in `on`

I'm trying to setup dependabot on a Github repo.

Here's my config file:

version: 2
updates:
  - package-ecosystem: "pip"
    directory: "/"
    schedule:
      interval: "daily"
    open-pull-requests-limit: 10

I'm getting the following error:

Annotations
1 error
Error : .github#L1
No event triggers defined in `on`

This error can occur in case of parsing error. But I adapted this file from a copy-paste of an example in the docs. Besides, I validated the yaml file with a validation tool.

Any idea what I'm doing wrong?