diff --git a/src/de/zbit/kegg/gui/SBMLModelSplitPane.java b/src/de/zbit/kegg/gui/SBMLModelSplitPane.java
index 92c05d8..5266022 100755
--- a/src/de/zbit/kegg/gui/SBMLModelSplitPane.java
+++ b/src/de/zbit/kegg/gui/SBMLModelSplitPane.java
@@ -225,6 +225,7 @@ public void valueChanged(TreeSelectionEvent e) {
 			}
 			setDividerLocation(proportionalLocation);
 		} else {
+		  System.out.println("node class " + node.getClass().getName() + " is unknown.");
 			// displayURL(helpURL);
 		}
 	}