Index: trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(revision 15948)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(revision 15949)
@@ -431,5 +431,5 @@
             canvasRules.clear();
             // remove "areaStyle" pseudo classes intended only for validator (causes StackOverflowError otherwise), see #16183
-            removeAreaStylePseudoClass = true;
+            removeAreaStylePseudoClass = url == null || !url.contains("validator"); // resource://data/validator/ or xxx.validator.mapcss
             try (InputStream in = getSourceInputStream()) {
                 try (Reader reader = new BufferedReader(UTFInputStreamReader.create(in))) {