diff --git a/denon/avrconnection.cpp b/denon/avrconnection.cpp
index e2016694..53c53123 100644
--- a/denon/avrconnection.cpp
+++ b/denon/avrconnection.cpp
@@ -41,10 +41,9 @@ AvrConnection::AvrConnection(const QHostAddress &hostAddress, const int &port, Q
     connect(m_socket, &QTcpSocket::connected, this, &AvrConnection::onConnected);
     connect(m_socket, &QTcpSocket::disconnected, this, &AvrConnection::onDisconnected);
     connect(m_socket, &QTcpSocket::readyRead, this, &AvrConnection::readData);
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(m_socket, &QTcpSocket::errorOccurred, this, &AvrConnection::onError);
 #else
-    // Note: error signal will be interpreted as function, not as signal in C++11
     connect(m_socket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(onError(QAbstractSocket::SocketError)));
 #endif
 
diff --git a/denon/heos.cpp b/denon/heos.cpp
index 2c179d17..406aaef9 100644
--- a/denon/heos.cpp
+++ b/denon/heos.cpp
@@ -50,7 +50,7 @@ Heos::Heos(const QHostAddress &hostAddress, QObject *parent) :
     connect(m_socket, &QTcpSocket::connected, this, &Heos::onConnected);
     connect(m_socket, &QTcpSocket::disconnected, this, &Heos::onDisconnected);
     connect(m_socket, &QTcpSocket::readyRead, this, &Heos::readData);
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(m_socket, &QTcpSocket::errorOccurred, this, &Heos::onError);
 #else
     connect(m_socket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(onError(QAbstractSocket::SocketError)));
diff --git a/eq-3/maxcube.cpp b/eq-3/maxcube.cpp
index e10da4ee..965d4e10 100644
--- a/eq-3/maxcube.cpp
+++ b/eq-3/maxcube.cpp
@@ -40,7 +40,7 @@ MaxCube::MaxCube(QObject *parent, QString serialNumber, QHostAddress hostAdress,
     connect(this, &MaxCube::stateChanged, this, &MaxCube::connectionStateChanged);
     connect(this, &MaxCube::readyRead, this, &MaxCube::onReadyRead);
     connect(this, &MaxCube::cubeDataAvailable, this, &MaxCube::processCubeData);
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(this, &MaxCube::errorOccurred, this, &MaxCube::onTcpError);
 #else
     connect(this, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(onTcpError(QAbstractSocket::SocketError)));
diff --git a/keba/kecontactdatalayer.cpp b/keba/kecontactdatalayer.cpp
index a60e5c1c..7e27c200 100644
--- a/keba/kecontactdatalayer.cpp
+++ b/keba/kecontactdatalayer.cpp
@@ -37,7 +37,7 @@ KeContactDataLayer::KeContactDataLayer(QObject *parent) : QObject(parent)
     m_udpSocket = new QUdpSocket(this);
     connect(m_udpSocket, &QUdpSocket::readyRead, this, &KeContactDataLayer::readPendingDatagrams);
     connect(m_udpSocket, &QUdpSocket::stateChanged, this, &KeContactDataLayer::onSocketStateChanged);
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5 , 15, 0)
     connect(m_udpSocket, &QUdpSocket::errorOccurred, this, &KeContactDataLayer::onSocketError);
 #else
     connect(m_udpSocket, SIGNAL(error(QAbstractSocket::SocketError)),this, SLOT(onSocketError(QAbstractSocket::SocketError)));
diff --git a/kodi/kodiconnection.cpp b/kodi/kodiconnection.cpp
index 20580677..45a2719b 100644
--- a/kodi/kodiconnection.cpp
+++ b/kodi/kodiconnection.cpp
@@ -43,7 +43,7 @@ KodiConnection::KodiConnection(const QHostAddress &hostAddress, int port, QObjec
 
     connect(m_socket, &QTcpSocket::connected, this, &KodiConnection::onConnected);
     connect(m_socket, &QTcpSocket::disconnected, this, &KodiConnection::onDisconnected);
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(m_socket, &QTcpSocket::errorOccurred, this, &KodiConnection::onError);
 #else
     connect(m_socket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(onError(QAbstractSocket::SocketError)));
diff --git a/mailnotification/smtpclient.cpp b/mailnotification/smtpclient.cpp
index cac5b5a5..6e497f31 100644
--- a/mailnotification/smtpclient.cpp
+++ b/mailnotification/smtpclient.cpp
@@ -42,7 +42,7 @@ SmtpClient::SmtpClient(QObject *parent):
     connect(m_socket, &QSslSocket::readyRead, this, &SmtpClient::readData);
     connect(m_socket, &QSslSocket::disconnected, this, &SmtpClient::disconnected);
     connect(m_socket, &QSslSocket::encrypted, this, &SmtpClient::onEncrypted);
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(m_socket, &QTcpSocket::errorOccurred, this, &SmtpClient::onSocketError);
 #else
     connect(m_socket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(onSocketError(QAbstractSocket::SocketError)));
diff --git a/serialportcommander/integrationpluginserialportcommander.cpp b/serialportcommander/integrationpluginserialportcommander.cpp
index 93feab53..32c4f156 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(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
         connect(serialPort, &QSerialPort::errorOccurred, this, &IntegrationPluginSerialPortCommander::onSerialError);
 #else
         connect(serialPort, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(onSerialError(QSerialPort::SerialPortError)));
diff --git a/tcpcommander/tcpserver.cpp b/tcpcommander/tcpserver.cpp
index 9b080378..5b6d3a3c 100644
--- a/tcpcommander/tcpserver.cpp
+++ b/tcpcommander/tcpserver.cpp
@@ -121,10 +121,9 @@ void TcpServer::newConnection()
     emit connectionCountChanged(m_clients.count());
     connect(socket, &QTcpSocket::disconnected, this, &TcpServer::onDisconnected);
     connect(socket, &QTcpSocket::readyRead, this, &TcpServer::readData);
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(socket, &QTcpSocket::errorOccurred, this, &TcpServer::onError);
 #else
-    // Note: error signal will be interpreted as function, not as signal in C++11
     connect(socket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(onError(QAbstractSocket::SocketError)));
 #endif
 }
diff --git a/usbrly82/usbrly82.cpp b/usbrly82/usbrly82.cpp
index 656d8efb..e06f6aa6 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(6,0,0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 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 3e2b77b3..b2f6d9dd 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(6, 0, 0)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
     connect(serialPort, &QSerialPort::errorOccurred, this, &IntegrationPluginWs2812fx::onSerialError);
 #else
     connect(serialPort, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(onSerialError(QSerialPort::SerialPortError)));