diff --git a/src/network/access/qrestreply.h b/src/network/access/qrestreply.h
index 02b6d1196d..b4616e7fb3 100644
--- a/src/network/access/qrestreply.h
+++ b/src/network/access/qrestreply.h
@@ -6,9 +6,15 @@
 
 #include <QtNetwork/qnetworkreply.h>
 
+#include <optional>
+
 QT_BEGIN_NAMESPACE
 
+class QByteArray;
 class QDebug;
+class QJsonDocument;
+class QString;
+
 class QRestReplyPrivate;
 class Q_NETWORK_EXPORT QRestReply : public QObject
 {