AWS GDK: Could not find artifact

I am trying to deploy docker containers to IoT devices using Greengrass. The docker-compose.yml file is stored inside of an s3 bucket. The IAM policies and Greengrass policies that I am using allow me to retrieve from s3 buckets.

My recipe.yaml looks like this:

---
RecipeFormatVersion: '2020-01-25'
ComponentName: com.example.DockerTest
ComponentVersion: '1.0.0'
ComponentDescription: 'Uses Greengrass to deploy NodeRed and Mosquitto to docker containers on the IoT defices.'
ComponentPublisher: Amazon
ComponentDependencies:
  aws.greengrass.DockerApplicationManager:
    VersionRequirement: ~2.0.0
Manifests:
  - Platform:
      os: all
    Lifecycle:
        run: docker-compose -f {artifacts:path}/docker-compose.yaml up
    Artifacts:
      - URI: "docker:nodered/node-red:latest"
      - URI: "docker:eclipse-mosquitto:latest"
      - URI: "s3://<bucket name>/docker-compose.yml"

My gdk-config.json looks like this:

{
  "component": {
    "com.example.DockerTest": {
      "author": "<custom author name>",
      "version": "1.0.0",
      "build": {
        "build_system": "zip"
      },
      "publish": {
        "bucket": "<bucket name>",
        "region": "<region>"
      }
    }
  },
  "gdk_version": "1.0.0"
}

Everything in angle brackets is valid, by the way - just left out for privacy.

However, whenever i run gdk component build where the component is specified, I get this error:

Exception: Could not find artifact with URI 's3://<bucket name>/docker-compose.yml' on s3 or inside the build folders

I made sure to specify the URI correctly, after copy + pasting it from s3. Why is this happening?