Index: /trunk/src/org/openstreetmap/josm/gui/mappaint/ElemStyles.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/mappaint/ElemStyles.java	(revision 15096)
+++ /trunk/src/org/openstreetmap/josm/gui/mappaint/ElemStyles.java	(revision 15097)
@@ -63,5 +63,5 @@
  */
 public class ElemStyles implements PreferenceChangedListener {
-    private final List<StyleSource> styleSources;
+    private final List<StyleSource> styleSources = Collections.synchronizedList(new ArrayList<>());
     private boolean drawMultipolygon;
 
@@ -74,5 +74,5 @@
     private short defaultLinesIdx;
 
-    private final Map<String, String> preferenceCache = new HashMap<>();
+    private final Map<String, String> preferenceCache = Collections.synchronizedMap(new HashMap<>());
 
     private volatile Color backgroundColorCache;
@@ -82,5 +82,4 @@
      */
     public ElemStyles() {
-        styleSources = new ArrayList<>();
         Config.getPref().addPreferenceChangeListener(this);
     }
Index: /trunk/test/unit/org/openstreetmap/josm/gui/preferences/map/TaggingPresetPreferenceTestIT.java
===================================================================
--- /trunk/test/unit/org/openstreetmap/josm/gui/preferences/map/TaggingPresetPreferenceTestIT.java	(revision 15096)
+++ /trunk/test/unit/org/openstreetmap/josm/gui/preferences/map/TaggingPresetPreferenceTestIT.java	(revision 15097)
@@ -23,4 +23,5 @@
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
 import org.junit.runners.Parameterized.Parameters;
 import org.openstreetmap.josm.TestUtils;
@@ -30,5 +31,4 @@
 import org.openstreetmap.josm.spi.preferences.Config;
 import org.openstreetmap.josm.testutils.JOSMTestRules;
-import org.openstreetmap.josm.testutils.ParallelParameterized;
 import org.openstreetmap.josm.tools.ImageProvider;
 import org.openstreetmap.josm.tools.Logging;
@@ -40,5 +40,5 @@
  * Integration tests of {@link TaggingPresetPreference} class.
  */
-@RunWith(ParallelParameterized.class)
+@RunWith(Parameterized.class)
 public class TaggingPresetPreferenceTestIT {