AWS S3 Generating Signed Urls ''AccessDenied''

I am using NodeJs to upload files to AWS S3. I want the client to be able to download the files securely. So I am trying to generate signed URLs, that expire after one usage. My code looks like this:

Uploading

const s3bucket = new AWS.S3({
    accessKeyId: 'my-access-key-id',
    secretAccessKey: 'my-secret-access-key',
    Bucket: 'my-bucket-name',
})
const uploadParams = {
    Body: file.data,
    Bucket: 'my-bucket-name',
    ContentType: file.mimetype,
    Key: `files/${file.name}`,
}
s3bucket.upload(uploadParams, function (err, data) {
    // ...
})

Downloading

const url = s3bucket.getSignedUrl('getObject', {
    Bucket: 'my-bucket-name',
    Key: 'file-key',
    Expires: 300,
})

Issue

When opening the URL I get the following:

This XML file does not appear to have any style information associated with it. The document tree is shown below.
<Error>
    <Code>AccessDenied</Code>
    <Message>
        There were headers present in the request which were not signed
    </Message>
    <HeadersNotSigned>host</HeadersNotSigned>
    <RequestId>D63C8ED4CD8F4E5F</RequestId>
    <HostId>
        9M0r2M3XkRU0JLn7cv5QN3S34G8mYZEy/v16c6JFRZSzDBa2UXaMLkHoyuN7YIt/LCPNnpQLmF4=
    </HostId>
</Error>

I coultn't manage to find the mistake. I would really appreciate any help :)

from AWS S3 Generating Signed Urls ''AccessDenied''