QNetworkDiskCache not caching

[goocreations]

I implemented a QNetworkDiskCache to cache files that are downloaded from my server. I used the example code in the documentation (http://doc.qt.io/qt-4.8/qnetworkdiskcache.html). However, every time a request a file, the request is retrieved from the network instead of the cache, or that is at least what is outputted here:

void Cacher::requestFinished(QNetworkReply* reply)
{
	QByteArray data=reply->readAll();
	QString str(data);

	qDebug() << "---------------------------------------------------";
	qDebug() << "Size:" << data.size();
	qDebug() << "Item Url:" << reply->url().toString();
	qDebug() << "Content Type:" << reply->header(QNetworkRequest::ContentTypeHeader).toString();
	QVariant fromCache = reply->attribute(QNetworkRequest::SourceIsFromCacheAttribute);
	qDebug() << "Item from cache?" << fromCache.toBool();
	qDebug() << "File Last Modified:" << reply->header(QNetworkRequest::LastModifiedHeader).toString();
}

And yes, I've set

request.setAttribute(QNetworkRequest::CacheLoadControlAttribute, QNetworkRequest::PreferCache);

I'm unsure why the file is never retrieved from the cache, so I set the following HTTP headers, just in case they are needed:

Cache-Control: max-age=31556926, private
Expires: 0

Does someone know why my files are never cached? Is there something else I have to set?

[goocreations]

Seems that my Apache server automatically set the HTTP header to Pragma: no-cache. Changed that and now caching is working.