QML Image tag for http URIs does not set Accept: header

If using QML Image {} Element with a source: URI of type HTTP, the Accept: header does not seem to be set correctly. Resulting in some servers returning "Not Acceptable". This is especially unfortunate, as QNetworkAccessManager does not allow adding headers to requests due to heavy use of 'const' - so there seems to be no legit way to fix this. (If there is, please advise).