diff --git a/src/test-runner/testsuite-ui/src/org/sbml/testsuite/ui/MainWindow.java b/src/test-runner/testsuite-ui/src/org/sbml/testsuite/ui/MainWindow.java
index 9f9758b5f5..2215895db0 100644
--- a/src/test-runner/testsuite-ui/src/org/sbml/testsuite/ui/MainWindow.java
+++ b/src/test-runner/testsuite-ui/src/org/sbml/testsuite/ui/MainWindow.java
@@ -3672,6 +3672,14 @@ private void updatePlotsForSelection(TreeItem treeItem)
 
         ResultSet expected = model.getSuite().get(itemName).getExpectedResult();
 
+        if (expected == null)
+        {
+            showMessageNotAvailable(cmpDifferences,
+                                    "Data cannot be plotted because the reference result is missing.");
+            cmpDifferences.layout();
+            return;
+        }
+
         if (expected.hasInfinityOrNaN())
         {
             showMessageNotAvailable(cmpDifferences,