Index: trunk/src/org/openstreetmap/josm/gui/layer/markerlayer/Marker.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/layer/markerlayer/Marker.java	(revision 14758)
+++ trunk/src/org/openstreetmap/josm/gui/layer/markerlayer/Marker.java	(revision 14759)
@@ -12,8 +12,8 @@
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 import javax.swing.ImageIcon;
@@ -79,5 +79,5 @@
         // will make gui for it so I'm keeping it here
 
-        private static final Map<String, TemplateEntryProperty> CACHE = new HashMap<>();
+        private static final Map<String, TemplateEntryProperty> CACHE = new ConcurrentHashMap<>();
 
         public static TemplateEntryProperty forMarker(String layerName) {