diff --git a/kcms/touchpad/src/backends/kwin_wayland/kwinwaylandbackend.h b/kcms/touchpad/src/backends/kwin_wayland/kwinwaylandbackend.h
--- a/kcms/touchpad/src/backends/kwin_wayland/kwinwaylandbackend.h
+++ b/kcms/touchpad/src/backends/kwin_wayland/kwinwaylandbackend.h
@@ -40,7 +40,7 @@
     bool getConfig() Q_DECL_OVERRIDE;
     bool getDefaultConfig() Q_DECL_OVERRIDE;
     bool isChangedConfig() const Q_DECL_OVERRIDE;
-    const QString &errorString() const Q_DECL_OVERRIDE { return m_errorString; }
+    QString errorString() const Q_DECL_OVERRIDE { return m_errorString; }
 
     virtual int touchpadCount() const Q_DECL_OVERRIDE { return m_devices.count(); }
     virtual QVector<QObject*> getDevices() const Q_DECL_OVERRIDE { return m_devices; }
diff --git a/kcms/touchpad/src/backends/x11/xlibbackend.h b/kcms/touchpad/src/backends/x11/xlibbackend.h
--- a/kcms/touchpad/src/backends/x11/xlibbackend.h
+++ b/kcms/touchpad/src/backends/x11/xlibbackend.h
@@ -52,7 +52,7 @@
     QStringList supportedParameters() const Q_DECL_OVERRIDE {
         return m_device ? m_device->supportedParameters() : QStringList();
     }
-    const QString &errorString() const Q_DECL_OVERRIDE { return m_errorString; }
+    QString errorString() const Q_DECL_OVERRIDE { return m_errorString; }
     int touchpadCount() const Q_DECL_OVERRIDE { return m_device ? 1 : 0; }
 
     void setTouchpadOff(TouchpadOffState) Q_DECL_OVERRIDE;
diff --git a/kcms/touchpad/src/touchpadbackend.h b/kcms/touchpad/src/touchpadbackend.h
--- a/kcms/touchpad/src/touchpadbackend.h
+++ b/kcms/touchpad/src/touchpadbackend.h
@@ -43,7 +43,7 @@
     virtual bool isChangedConfig() const {return false;}
 
     virtual QStringList supportedParameters() const {return QStringList();}
-    virtual const QString &errorString() const {return QString();}
+    virtual QString errorString() const {return QString();}
 
     virtual QVector<QObject*> getDevices() const { return QVector<QObject*>(); }
     virtual int touchpadCount() const {return 0;}