Index: trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 15912)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 15913)
@@ -372,5 +372,5 @@
         if (!newSel.isEmpty()) {
             final LatLon center = newSel.iterator().next().getBBox().getCenter();
-            Territories.getRegionalTaginfoUrls(center)
+            Territories.getRegionalTaginfoUrls(center).stream()
                     .map(taginfo -> new TaginfoAction(
                             tagTable, editHelper::getDataKey, editHelper::getDataValues,
Index: trunk/src/org/openstreetmap/josm/tools/Territories.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/Territories.java	(revision 15912)
+++ trunk/src/org/openstreetmap/josm/tools/Territories.java	(revision 15913)
@@ -10,4 +10,5 @@
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -203,7 +204,7 @@
      * @since 15876
      */
-    public static Stream<TaginfoRegionalInstance> getRegionalTaginfoUrls(LatLon ll) {
+    public static List<TaginfoRegionalInstance> getRegionalTaginfoUrls(LatLon ll) {
         if (iso3166Cache == null) {
-            return Stream.empty();
+            return Collections.emptyList();
         }
         return iso3166Cache.entrySet().parallelStream().distinct()
@@ -212,5 +213,6 @@
                 .distinct()
                 .flatMap(code -> Stream.of(taginfoCache, taginfoGeofabrikCache).map(cache -> cache.get(code)))
-                .filter(Objects::nonNull);
+                .filter(Objects::nonNull)
+                .collect(Collectors.toList());
     }
 }