QWebsocket Server error in QT 5.15

[Kutyus]

Hi!
I upgraded from 5.13.2 to 5.15.0 and when compiling qwebsocketserver the following errors occur:

wscom.cpp:30:40: error: ‘SecureMode’ is not a member of ‘QWebSocketServer’
  wssrv = new QWebSocketServer("alice", QWebSocketServer::SecureMode, this);
                                        ^~~~~~~~~~~~~~~~
wscom.cpp:32:20: error: aggregate ‘QSslConfiguration sslConfig’ has incomplete type and cannot be defined
  QSslConfiguration sslConfig;
                    ^~~~~~~~~
wscom.cpp:38:19: error: variable ‘QSslKey sslKey’ has initializer but incomplete type
     QSslKey sslKey(&keyFile, QSsl::Rsa, QSsl::Pem);
                   ^
wscom.cpp:41:33: error: ‘QSslSocket’ has not been declared
     sslConfig.setPeerVerifyMode(QSslSocket::VerifyNone);
                                 ^~~~~~~~~~
wscom.cpp:46:9: error: ‘class QWebSocketServer’ has no member named ‘setSslConfiguration’
  wssrv->setSslConfiguration(sslConfig);
         ^~~~~~~~~~~~~~~~~~~

I compile on Raspberry PI, Debian Linux. Any ideas?
Thanks in advance!