diff --git a/kcmkwin/kwincompositing/compositing.cpp b/kcmkwin/kwincompositing/compositing.cpp
index 192e3b1026..d91d2a51a0 100644
--- a/kcmkwin/kwincompositing/compositing.cpp
+++ b/kcmkwin/kwincompositing/compositing.cpp
@@ -37,7 +37,7 @@ Compositing::Compositing(QObject *parent)
 {
 }
 
-bool Compositing::OpenGLIsUnsafe()
+bool Compositing::OpenGLIsUnsafe() const
 {
     KConfigGroup kwinConfig(KSharedConfig::openConfig("kwinrc"), "Compositing");
     return kwinConfig.readEntry("OpenGLIsUnsafe", true);
diff --git a/kcmkwin/kwincompositing/compositing.h b/kcmkwin/kwincompositing/compositing.h
index 037cef006c..25e7faa4f0 100644
--- a/kcmkwin/kwincompositing/compositing.h
+++ b/kcmkwin/kwincompositing/compositing.h
@@ -36,7 +36,7 @@ class Compositing : public QObject
 public:
     explicit Compositing(QObject *parent = 0);
 
-    Q_INVOKABLE bool OpenGLIsUnsafe();
+    Q_INVOKABLE bool OpenGLIsUnsafe() const;
     Q_INVOKABLE bool OpenGLIsBroken();
 
 private: