Confluence Server API minorEdit Flag does not work?

As described on{id}/child/attachment-updateData, the Confluence API allows you to pass the flag minorEdit as one part of a multipart/form-data POST request when updating the binary data stored as an attachment to a Confluence page.

This should have the following effect:

“If an update is considered to be a minor edit, notifications will not be sent to the watchers of that content.”

We are passing “minorEdit=true” and can clearly see in the response from the Server that this is received and returned to us in the json as “minorEdit: true”. Still watchers of the page receive E-Mail notifications that we would not like to be sent.

Any experience with this kind of problem? Are we doing something wrong or is this a known bug?