Index: trunk/src/org/openstreetmap/josm/tools/I18n.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/I18n.java	(revision 17181)
+++ trunk/src/org/openstreetmap/josm/tools/I18n.java	(revision 17182)
@@ -421,5 +421,5 @@
             return;
         final ZipEntry enfile = new ZipEntry(PLUGIN_TRANS_DIRECTORY + "en.lang");
-        final ZipEntry langfile = new ZipEntry(PLUGIN_TRANS_DIRECTORY + loadedCode + ".lang");
+        final ZipEntry langfile = new ZipEntry(PLUGIN_TRANS_DIRECTORY + loadedCode.replace('@', '-') + ".lang");
         try (
             ZipFile zipFile = new ZipFile(source, StandardCharsets.UTF_8);