Index: src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java
===================================================================
--- src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(revision 15060)
+++ src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(working copy)
@@ -69,6 +69,8 @@
 import org.openstreetmap.josm.gui.mappaint.mapcss.MapCSSStyleSource.MapCSSRuleIndex;
 import org.openstreetmap.josm.gui.mappaint.mapcss.Selector;
 import org.openstreetmap.josm.gui.mappaint.mapcss.Selector.AbstractSelector;
+import org.openstreetmap.josm.gui.mappaint.mapcss.Selector.ChildOrParentSelector;
+import org.openstreetmap.josm.gui.mappaint.mapcss.Selector.ChildOrParentSelectorType;
 import org.openstreetmap.josm.gui.mappaint.mapcss.Selector.GeneralSelector;
 import org.openstreetmap.josm.gui.mappaint.mapcss.Selector.OptimizedGeneralSelector;
 import org.openstreetmap.josm.gui.mappaint.mapcss.parsergen.MapCSSParser;
@@ -854,6 +856,17 @@
         while (candidates.hasNext()) {
             MapCSSRule r = candidates.next();
             env.clearSelectorMatchingInformation();
+            if (partialSelection && r.selector instanceof Selector.ChildOrParentSelector) {
+                ChildOrParentSelector sel = (Selector.ChildOrParentSelector) r.selector;
+                if (sel.type == ChildOrParentSelectorType.ELEMENT_OF && p.getDataSet() != null) {
+                    List<OsmPrimitive> toCheck = new ArrayList<>();
+                    toCheck.addAll(p.getDataSet().searchWays(p.getBBox()));
+                    toCheck.addAll(p.getDataSet().searchRelations(p.getBBox()));
+                    toCheck.removeIf(OsmPrimitive::isSelected);
+                    Set<Set<TagCheck>> checksCol = Collections.singleton(Collections.singleton(indexData.getCheck(r)));
+                    toCheck.forEach(p2 -> res.addAll(getErrorsForPrimitive(p2, includeOtherSeverity, checksCol)));
+                }
+            }
             if (r.selector.matches(env)) { // as side effect env.parent will be set (if s is a child selector)
                 TagCheck check = indexData.getCheck(r);
                 if (check != null) {