Index: applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/FindRelationAction.java
===================================================================
--- applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/FindRelationAction.java	(revision 35195)
+++ applications/editors/josm/plugins/reltoolbox/src/relcontext/actions/FindRelationAction.java	(revision 35196)
@@ -179,5 +179,5 @@
                             for (String key : r.keySet()) {
                                 if (key.contains(keywords[i]) || r.get(key).toLowerCase().contains(keywords[i])
-                                        || tr(r.get(key)).toLowerCase().contains(keywords[i])) {
+                                        || safetr(r.get(key)).toLowerCase().contains(keywords[i])) {
                                     ok = true;
                                     break;
@@ -200,4 +200,13 @@
     }
 
+    private static String safetr(String s) {
+        try {
+            return tr(s);
+        } catch (IllegalArgumentException e) {
+            Logging.trace(e);
+            return s;
+        }
+    }
+
     /**
      * I admit, some of it was copypasted from {@link org.openstreetmap.josm.gui.dialogs.RelationListDialog.RelationListModel}.