Index: src/org/openstreetmap/josm/data/validation/tests/TagChecker.java
===================================================================
--- src/org/openstreetmap/josm/data/validation/tests/TagChecker.java	(revision 18280)
+++ src/org/openstreetmap/josm/data/validation/tests/TagChecker.java	(working copy)
@@ -544,9 +544,9 @@
      *  else a set which might be empty.
      */
     private static Set<String> getPresetValues(String key) {
-        Set<String> res = TaggingPresets.getPresetValues(key);
-        if (!Utils.isEmpty(res))
-            return res;
+        if (isKeyInPresets(key)) {
+            return TaggingPresets.getPresetValues(key);
+        }
         if (additionalPresetsValueData.contains(key))
             return Collections.emptySet();
         // null means key is not known
@@ -560,7 +560,7 @@
      * @since 9023
      */
     public static boolean isKeyInPresets(String key) {
-        return !Utils.isEmpty(TaggingPresets.getPresetValues(key));
+        return TaggingPresets.getPresetKeys().contains(key);
     }
 
     /**