Index: trunk/src/org/openstreetmap/josm/data/validation/tests/UnclosedWays.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/tests/UnclosedWays.java	(revision 17489)
+++ trunk/src/org/openstreetmap/josm/data/validation/tests/UnclosedWays.java	(revision 17491)
@@ -98,5 +98,5 @@
                 final Severity severity;
                 // see #20455: raise severity to error when we are sure that tag key must describe an area
-                if (ignore && !specialValues.isEmpty()) {
+                if (ignore && !specialValues.isEmpty() || "boundary".equals(key)) {
                     severity = Severity.WARNING;
                 } else {