Index: trunk/src/org/openstreetmap/josm/data/projection/Projections.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/projection/Projections.java	(revision 18025)
+++ trunk/src/org/openstreetmap/josm/data/projection/Projections.java	(revision 18028)
@@ -14,4 +14,5 @@
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Supplier;
 import java.util.regex.Matcher;
@@ -85,5 +86,5 @@
     private static final Set<String> allCodes = new HashSet<>();
     private static final Map<String, Supplier<Projection>> projectionSuppliersByCode = new HashMap<>();
-    private static final Map<String, Projection> projectionsByCodeCache = new HashMap<>();
+    private static final Map<String, Projection> projectionsByCodeCache = new ConcurrentHashMap<>();
 
     /*********************************