Index: trunk/data/validator/geometry.mapcss
===================================================================
--- trunk/data/validator/geometry.mapcss	(revision 13379)
+++ trunk/data/validator/geometry.mapcss	(revision 13394)
@@ -306,4 +306,9 @@
 }
 
+/* #15648 */
+way[place=island]!:closed {
+  throwError: tr("Way with {1} not closed.", "{0.tag}");
+}
+
 /* #12561 - building larger than Aalsmeer Flower Auction (518000) and Tesla factory (510000) */
 area:closed[building][building!=no][eval(areasize()) > 520000] {