diff --git a/src/app/application.cpp b/src/app/application.cpp
index 0a421670a..7eb98c0d8 100644
--- a/src/app/application.cpp
+++ b/src/app/application.cpp
@@ -660,7 +660,7 @@ void Application::shutdownCleanup(QSessionManager &manager)
     // According to the qt docs we shouldn't call quit() inside a slot.
     // aboutToQuit() is never emitted if the user hits "Cancel" in
     // the above dialog.
-    QTimer::singleShot(0, qApp, SLOT(quit()));
+    QTimer::singleShot(0, qApp, &QCoreApplication::quit);
 }
 #endif
 
diff --git a/src/app/main.cpp b/src/app/main.cpp
index fb37fa43f..524b80036 100644
--- a/src/app/main.cpp
+++ b/src/app/main.cpp
@@ -329,7 +329,7 @@ void showSplashScreen()
     painter.drawText(224 - painter.fontMetrics().width(version), 270, version);
     QSplashScreen *splash = new QSplashScreen(splash_img);
     splash->show();
-    QTimer::singleShot(1500, splash, SLOT(deleteLater()));
+    QTimer::singleShot(1500, splash, &QObject::deleteLater);
     qApp->processEvents();
 }
 
diff --git a/src/base/net/reverseresolution.cpp b/src/base/net/reverseresolution.cpp
index c639e9cbc..15c593776 100644
--- a/src/base/net/reverseresolution.cpp
+++ b/src/base/net/reverseresolution.cpp
@@ -65,7 +65,11 @@ void ReverseResolution::resolve(const QString &ip)
     }
     else {
         // Actually resolve the ip
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 9, 0))
+        m_lookups.insert(QHostInfo::lookupHost(ip, this, &ReverseResolution::hostResolved), ip);
+#else
         m_lookups.insert(QHostInfo::lookupHost(ip, this, SLOT(hostResolved(QHostInfo))), ip);
+#endif
     }
 }
 
diff --git a/src/gui/mainwindow.cpp b/src/gui/mainwindow.cpp
index 05a0580a1..fb18375a5 100644
--- a/src/gui/mainwindow.cpp
+++ b/src/gui/mainwindow.cpp
@@ -375,7 +375,7 @@ MainWindow::MainWindow(QWidget *parent)
     on_actionWarningMessages_triggered(m_ui->actionWarningMessages->isChecked());
     on_actionCriticalMessages_triggered(m_ui->actionCriticalMessages->isChecked());
     if (m_ui->actionSearchWidget->isChecked())
-        QTimer::singleShot(0, this, SLOT(on_actionSearchWidget_triggered()));
+        QTimer::singleShot(0, this, &MainWindow::on_actionSearchWidget_triggered);
 
     // Auto shutdown actions
     QActionGroup *autoShutdownGroup = new QActionGroup(this);
@@ -1213,7 +1213,7 @@ bool MainWindow::event(QEvent *e)
                 if (!hasModalWindow) {
                     qDebug("Minimize to Tray enabled, hiding!");
                     e->ignore();
-                    QTimer::singleShot(0, this, SLOT(hide()));
+                    QTimer::singleShot(0, this, &QWidget::hide);
                     return true;
                 }
             }