diff --git a/libnymea-core/hardware/modbus/modbusrtumasterimpl.cpp b/libnymea-core/hardware/modbus/modbusrtumasterimpl.cpp
index 356f0d87..3a4922fe 100644
--- a/libnymea-core/hardware/modbus/modbusrtumasterimpl.cpp
+++ b/libnymea-core/hardware/modbus/modbusrtumasterimpl.cpp
@@ -54,7 +54,12 @@ ModbusRtuMasterImpl::ModbusRtuMasterImpl(const QUuid &modbusUuid, const QString
     m_timeout(timeout)
 {
 #ifdef WITH_QTSERIALBUS
+
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    m_modbus = new QModbusRtuSerialClient(this);
+#else
     m_modbus = new QModbusRtuSerialMaster(this);
+#endif
     m_modbus->setConnectionParameter(QModbusDevice::SerialPortNameParameter, m_serialPort);
     m_modbus->setConnectionParameter(QModbusDevice::SerialBaudRateParameter, m_baudrate);
     m_modbus->setConnectionParameter(QModbusDevice::SerialDataBitsParameter, m_dataBits);
@@ -63,7 +68,11 @@ ModbusRtuMasterImpl::ModbusRtuMasterImpl(const QUuid &modbusUuid, const QString
     m_modbus->setNumberOfRetries(m_numberOfRetries);
     m_modbus->setTimeout(m_timeout);
 
-    connect(m_modbus, &QModbusTcpClient::stateChanged, this, [=](QModbusDevice::State state){
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    connect(m_modbus, &QModbusRtuSerialClient::stateChanged, this, [=](QModbusDevice::State state){
+#else
+    connect(m_modbus, &QModbusRtuSerialMaster::stateChanged, this, [=](QModbusDevice::State state){
+#endif
         qCDebug(dcModbusRtu()) << "Connection state changed" << m_modbusUuid.toString() << m_serialPort << state;
         if (state == QModbusDevice::ConnectedState) {
             if (m_connected != true) {
@@ -78,7 +87,11 @@ ModbusRtuMasterImpl::ModbusRtuMasterImpl(const QUuid &modbusUuid, const QString
         }
     });
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    connect(m_modbus, &QModbusRtuSerialClient::errorOccurred, this, [=](QModbusDevice::Error error){
+#else
     connect(m_modbus, &QModbusRtuSerialMaster::errorOccurred, this, [=](QModbusDevice::Error error){
+#endif
         qCWarning(dcModbusRtu()) << "Error occurred for modbus RTU master" << m_modbusUuid.toString() << m_serialPort << error << m_modbus->errorString();
         if (error != QModbusDevice::NoError) {
             disconnectDevice();
diff --git a/libnymea-core/hardware/modbus/modbusrtumasterimpl.h b/libnymea-core/hardware/modbus/modbusrtumasterimpl.h
index 559b4fb9..dc09deea 100644
--- a/libnymea-core/hardware/modbus/modbusrtumasterimpl.h
+++ b/libnymea-core/hardware/modbus/modbusrtumasterimpl.h
@@ -93,9 +93,15 @@ private:
     bool m_connected = false;
 
 #ifdef WITH_QTSERIALBUS
+
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    QModbusRtuSerialClient *m_modbus = nullptr;
+#else
     QModbusRtuSerialMaster *m_modbus = nullptr;
 #endif
 
+#endif // WITH_QTSERIALBUS
+
     QString m_serialPort;
     qint32 m_baudrate;
     QSerialPort::Parity m_parity;
diff --git a/libnymea-core/libnymea-core.pro b/libnymea-core/libnymea-core.pro
index e1c9dc9a..dd951c14 100644
--- a/libnymea-core/libnymea-core.pro
+++ b/libnymea-core/libnymea-core.pro
@@ -21,14 +21,14 @@ packagesExist(systemd) {
 greaterThan(QT_MAJOR_VERSION, 5) {
     qtHaveModule(serialbus) {
         message("Building with QtSerialBus support.")
-        QT *= serialbus
+        QT += serialbus
         DEFINES += WITH_QTSERIALBUS
     } else {
         message("QtSerialBus package not found. Building without QtSerialBus support.")
     }
 
     # Separate module in Qt6
-    QT *= concurrent
+    QT += concurrent
 } else {
     packagesExist(Qt5SerialBus) {
         message("Building with QtSerialBus support.")
diff --git a/server/server.pro b/server/server.pro
index 08ba9f7a..3fdeb7ee 100644
--- a/server/server.pro
+++ b/server/server.pro
@@ -11,9 +11,9 @@ INSTALLS += target
 QT += sql websockets bluetooth dbus network
 
 greaterThan(QT_MAJOR_VERSION, 5) {
-    QT *= core5compat
+    QT += core5compat
 } else {
-    QT *= xml
+    QT += xml
 }
 
 CONFIG += link_pkgconfig
diff --git a/tests/auto/mqttbroker/mqttbroker.pro b/tests/auto/mqttbroker/mqttbroker.pro
index 5e19f1eb..b57cdc29 100644
--- a/tests/auto/mqttbroker/mqttbroker.pro
+++ b/tests/auto/mqttbroker/mqttbroker.pro
@@ -2,9 +2,9 @@ include(../../../nymea.pri)
 include(../autotests.pri)
 
 greaterThan(QT_MAJOR_VERSION, 5) {
-    QT *= core5compat
+    QT += core5compat
 } else {
-    QT *= xml
+    QT += xml
 }
 
 PKGCONFIG += nymea-mqtt
diff --git a/tests/auto/webserver/webserver.pro b/tests/auto/webserver/webserver.pro
index 85c57a2b..8f40ebc1 100644
--- a/tests/auto/webserver/webserver.pro
+++ b/tests/auto/webserver/webserver.pro
@@ -2,9 +2,9 @@ include(../../../nymea.pri)
 include(../autotests.pri)
 
 greaterThan(QT_MAJOR_VERSION, 5) {
-    QT *= core5compat
+    QT += core5compat
 } else {
-    QT *= xml
+    QT += xml
 }
 
 
diff --git a/tests/testlib/testlib.pro b/tests/testlib/testlib.pro
index bae6cc8b..4d5b0180 100644
--- a/tests/testlib/testlib.pro
+++ b/tests/testlib/testlib.pro
@@ -11,14 +11,14 @@ PKGCONFIG += nymea-zigbee
 greaterThan(QT_MAJOR_VERSION, 5) {
     qtHaveModule(serialbus) {
         message("Building with QtSerialBus support.")
-        QT *= serialbus
+        QT += serialbus
         DEFINES += WITH_QTSERIALBUS
     } else {
         message("QtSerialBus package not found. Building without QtSerialBus support.")
     }
 
     # Separate module in Qt6
-    QT *= concurrent
+    QT += concurrent
 } else {
     packagesExist(Qt5SerialBus) {
         message("Building with QtSerialBus support.")