Index: trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 15668)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 15669)
@@ -28,5 +28,4 @@
 import java.util.TreeSet;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.stream.Collectors;
 
 import javax.swing.AbstractAction;
@@ -372,6 +371,6 @@
                         membershipTable, x -> (IRelation<?>) membershipData.getValueAt(x, 0), e.getValue(), e.getKey()));
             }
-            membershipMenuTagInfoNatItems.addAll(taginfoNationalActions.stream().map(membershipMenu::add).collect(Collectors.toList()));
-            tagMenuTagInfoNatItems.addAll(taginfoNationalActions.stream().map(tagMenu::add).collect(Collectors.toList()));
+            taginfoNationalActions.stream().map(membershipMenu::add).forEach(membershipMenuTagInfoNatItems::add);
+            taginfoNationalActions.stream().map(tagMenu::add).forEach(tagMenuTagInfoNatItems::add);
         }
     }