diff --git a/helpers/killer/killer.cpp b/helpers/killer/killer.cpp
--- a/helpers/killer/killer.cpp
+++ b/helpers/killer/killer.cpp
@@ -40,6 +40,7 @@
     KLocalizedString::setApplicationDomain("kwin");
     qputenv("QT_QPA_PLATFORM", QByteArrayLiteral("xcb"));
     QApplication app(argc, argv);
+    app.setAttribute(Qt::AA_UseHighDpiPixmaps, true);
     QApplication::setWindowIcon(QIcon::fromTheme(QStringLiteral("dialog-warning")));
     QCoreApplication::setApplicationName(QStringLiteral("kwin_killer_helper"));
     QCoreApplication::setOrganizationDomain(QStringLiteral("kde.org"));
diff --git a/kcmkwin/kwinrules/main.cpp b/kcmkwin/kwinrules/main.cpp
--- a/kcmkwin/kwinrules/main.cpp
+++ b/kcmkwin/kwinrules/main.cpp
@@ -237,6 +237,7 @@
 KWIN_EXPORT int kdemain(int argc, char* argv[])
 {
     QApplication app(argc, argv);
+    app.setAttribute(Qt::AA_UseHighDpiPixmaps, true);
     app.setApplicationDisplayName(i18n("KWin"));
     app.setApplicationName("kwin_rules_dialog");
     app.setApplicationVersion("1.0");