Index: resources/data/validator/geometry.mapcss
===================================================================
--- resources/data/validator/geometry.mapcss	(revision 17678)
+++ resources/data/validator/geometry.mapcss	(working copy)
@@ -197,8 +197,10 @@
 
 /* Water area inside water area (spatial test) */
 area:closed:areaStyle[natural =~ /^(water|wetland|coastline)$/] ⊆  area:closed:areaStyle.water_area,
+area:closed:areaStyle[waterway=riverbank]                       ⊆  area:closed:areaStyle.water_area,
 area:closed:areaStyle[landuse=reservoir]                        ⊆  area:closed:areaStyle.water_area,
 area:closed:areaStyle[natural =~ /^(water|wetland|coastline)$/] ⊇  area:closed:areaStyle.water_area,
+area:closed:areaStyle[waterway=riverbank]                       ⊇  area:closed:areaStyle.water_area,
 area:closed:areaStyle[landuse=reservoir]                        ⊇  area:closed:areaStyle.water_area {
   throwWarning: tr("Water area inside water area");
 }