diff --git a/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java b/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java
index 0eb58965b..6d18af7d7 100644
--- a/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java
+++ b/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java
@@ -169,7 +169,8 @@ public class CircuitComponent extends JComponent {
      * @param drawables the list of drawables
      */
     public void addHighLighted(Collection<? extends Drawable> drawables) {
-        highLighted.addAll(drawables);
+        if (drawables != null)
+            highLighted.addAll(drawables);
     }
 
     /**