Index: trunk/src/org/openstreetmap/josm/gui/dialogs/validator/ValidatorTreePanel.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/validator/ValidatorTreePanel.java	(revision 11126)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/validator/ValidatorTreePanel.java	(revision 11127)
@@ -181,6 +181,7 @@
             = errors.stream().filter(filterToUse).collect(
                     Collectors.groupingBy(TestError::getSeverity, () -> new EnumMap<>(Severity.class),
-                            Collectors.groupingBy(e -> e.getDescription() == null ? "" : e.getDescription(),
-                                    Collectors.groupingBy(TestError::getMessage))));
+                            Collectors.groupingBy(TestError::getMessage,
+                                    Collectors.groupingBy(e -> e.getDescription() == null ? "" : e.getDescription()
+                                    ))));
 
         List<TreePath> expandedPaths = new ArrayList<>();