diff --git a/src/plasma/theme.cpp b/src/plasma/theme.cpp
--- a/src/plasma/theme.cpp
+++ b/src/plasma/theme.cpp
@@ -59,8 +59,8 @@
 
     d->settingsChanged(false);
     if (QCoreApplication::instance()) {
-        connect(QCoreApplication::instance(), SIGNAL(aboutToQuit()),
-                d, SLOT(onAppExitCleanup()));
+        connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit,
+                d, &ThemePrivate::onAppExitCleanup);
     }
     connect(d, &ThemePrivate::themeChanged, this, &Theme::themeChanged);
     connect(d, &ThemePrivate::defaultFontChanged, this, &Theme::defaultFontChanged);
@@ -85,8 +85,8 @@
     d->cacheTheme = useCache;
     d->fixedName = true;
     if (QCoreApplication::instance()) {
-        connect(QCoreApplication::instance(), SIGNAL(aboutToQuit()),
-                d, SLOT(onAppExitCleanup()));
+        connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit,
+                d, &ThemePrivate::onAppExitCleanup);
     }
     connect(d, &ThemePrivate::themeChanged, this, &Theme::themeChanged);
 }
@@ -131,8 +131,8 @@
         ThemePrivate::themesRefCount[themeName].ref();
         d = ThemePrivate::themes[themeName];
         if (QCoreApplication::instance()) {
-            connect(QCoreApplication::instance(), SIGNAL(aboutToQuit()),
-                    d, SLOT(onAppExitCleanup()));
+            connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit,
+                    d, &ThemePrivate::onAppExitCleanup);
         }
         connect(d, &ThemePrivate::themeChanged, this, &Theme::themeChanged);
     }