diff --git a/krunner/main.cpp b/krunner/main.cpp
--- a/krunner/main.cpp
+++ b/krunner/main.cpp
@@ -44,9 +44,14 @@
     qunsetenv("QT_DEVICE_PIXEL_RATIO");
     QCoreApplication::setAttribute(Qt::AA_DisableHighDpiScaling);
 
+    const bool qpaVariable = qEnvironmentVariableIsSet("QT_QPA_PLATFORM");
     KWorkSpace::detectPlatform(argc, argv);
     QQuickWindow::setDefaultAlphaBuffer(true);
     QApplication app(argc, argv);
+    if (!qpaVariable) {
+        // don't leak the env variable to processes we start
+        qunsetenv("QT_QPA_PLATFORM");
+    }
     KLocalizedString::setApplicationDomain("krunner");
 
     KQuickAddons::QtQuickSettings::init();
diff --git a/shell/main.cpp b/shell/main.cpp
--- a/shell/main.cpp
+++ b/shell/main.cpp
@@ -59,8 +59,13 @@
 
     QQuickWindow::setDefaultAlphaBuffer(true);
 
+    const bool qpaVariable = qEnvironmentVariableIsSet("QT_QPA_PLATFORM");
     KWorkSpace::detectPlatform(argc, argv);
     QApplication app(argc, argv);
+    if (!qpaVariable) {
+        // don't leak the env variable to processes we start
+        qunsetenv("QT_QPA_PLATFORM");
+    }
     KLocalizedString::setApplicationDomain("plasmashell");
 
     // The executable's path is added to the library/plugin paths.
diff --git a/startkde/startplasmacompositor.cmake b/startkde/startplasmacompositor.cmake
--- a/startkde/startplasmacompositor.cmake
+++ b/startkde/startplasmacompositor.cmake
@@ -218,10 +218,6 @@
 XDG_CURRENT_DESKTOP=KDE
 export XDG_CURRENT_DESKTOP
 
-#enforce wayland QPA
-QT_QPA_PLATFORM=wayland
-export QT_QPA_PLATFORM
-
 # kwin_wayland can possibly also start dbus-activated services which need env variables.
 # In that case, the update in startplasma might be too late.
 if which dbus-update-activation-environment >/dev/null 2>/dev/null ; then