--- old/src/java.base/share/classes/java/util/IllformedLocaleException.java	2019-08-27 17:29:02.418324386 -0700
+++ new/src/java.base/share/classes/java/util/IllformedLocaleException.java	2019-08-27 17:29:02.234324386 -0700
@@ -41,6 +41,7 @@
  */
 public class IllformedLocaleException extends RuntimeException {
 
+    @java.io.Serial
     private static final long serialVersionUID = -5245986824925681401L;
 
     private int _errIdx = -1;