diff --git a/effects/highlightwindow/highlightwindow.cpp b/effects/highlightwindow/highlightwindow.cpp
index 1e9f15e427..8e78b027ce 100644
--- a/effects/highlightwindow/highlightwindow.cpp
+++ b/effects/highlightwindow/highlightwindow.cpp
@@ -240,7 +240,8 @@ void HighlightWindowEffect::prepareHighlighting()
     foreach (EffectWindow * w, effects->stackingOrder())
     if (!m_windowOpacity.contains(w))    // Just in case we are still finishing from last time
         m_windowOpacity[w] = isInitiallyHidden(w) ? 0.0 : 1.0;
-    m_highlightedWindows.at(0)->addRepaintFull();
+    if (!m_highlightedWindows.isEmpty())
+        m_highlightedWindows.at(0)->addRepaintFull();
 }
 
 void HighlightWindowEffect::finishHighlighting()