diff --git a/evbox/evboxport.cpp b/evbox/evboxport.cpp
index 9f8114c5..c3a1bec5 100644
--- a/evbox/evboxport.cpp
+++ b/evbox/evboxport.cpp
@@ -48,7 +48,7 @@ EVBoxPort::EVBoxPort(const QString &portName, QObject *parent)
     m_serialPort->setParity(QSerialPort::NoParity);
 
     connect(m_serialPort, &QSerialPort::readyRead, this, &EVBoxPort::onReadyRead);
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 8, 0)
     connect(m_serialPort, &QSerialPort::errorOccurred, this, [this](){
 #else
     connect(m_serialPort, static_cast<void(QSerialPort::*)(QSerialPort::SerialPortError)>(&QSerialPort::error), this, [=](){
diff --git a/serialportcommander/integrationpluginserialportcommander.cpp b/serialportcommander/integrationpluginserialportcommander.cpp
index 32c4f156..3acbf483 100644
--- a/serialportcommander/integrationpluginserialportcommander.cpp
+++ b/serialportcommander/integrationpluginserialportcommander.cpp
@@ -109,7 +109,7 @@ void IntegrationPluginSerialPortCommander::setupThing(ThingSetupInfo *info)
             return info->finish(Thing::ThingErrorHardwareFailure, QT_TR_NOOP("Could not open serial port."));
         }
 
-#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 8, 0)
         connect(serialPort, &QSerialPort::errorOccurred, this, &IntegrationPluginSerialPortCommander::onSerialError);
 #else
         connect(serialPort, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(onSerialError(QSerialPort::SerialPortError)));
diff --git a/tplink/integrationplugintplink.cpp b/tplink/integrationplugintplink.cpp
index f0cabcf4..6ec038fd 100644
--- a/tplink/integrationplugintplink.cpp
+++ b/tplink/integrationplugintplink.cpp
@@ -423,7 +423,7 @@ void IntegrationPluginTPLink::connectToDevice(Thing *thing, const QHostAddress &
         fetchState(thing);
     });
 
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(socket, &QTcpSocket::errorOccurred, this, [](QAbstractSocket::SocketError error){
 #else
     typedef void (QTcpSocket:: *errorSignal)(QAbstractSocket::SocketError);
diff --git a/usbrly82/usbrly82.cpp b/usbrly82/usbrly82.cpp
index e06f6aa6..dc975ae7 100644
--- a/usbrly82/usbrly82.cpp
+++ b/usbrly82/usbrly82.cpp
@@ -192,7 +192,7 @@ bool UsbRly82::connectRelay(const QString &serialPort)
     }
 
     connect(m_serialPort, &QSerialPort::readyRead, this, &UsbRly82::onReadyRead);
-#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 8, 0)
     connect(m_serialPort, &QSerialPort::errorOccurred, this, &UsbRly82::onError, Qt::QueuedConnection);
 #else
     connect(m_serialPort, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(onError(QSerialPort::SerialPortError)), Qt::QueuedConnection);
diff --git a/ws2812fx/integrationpluginws2812fx.cpp b/ws2812fx/integrationpluginws2812fx.cpp
index b2f6d9dd..8aab821e 100644
--- a/ws2812fx/integrationpluginws2812fx.cpp
+++ b/ws2812fx/integrationpluginws2812fx.cpp
@@ -78,7 +78,7 @@ void IntegrationPluginWs2812fx::setupThing(ThingSetupInfo *info)
         return info->finish(Thing::ThingErrorHardwareFailure, QT_TR_NOOP("Error opening serial port."));
     }
 
-#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 8, 0)
     connect(serialPort, &QSerialPort::errorOccurred, this, &IntegrationPluginWs2812fx::onSerialError);
 #else
     connect(serialPort, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(onSerialError(QSerialPort::SerialPortError)));