src/java.base/share/classes/java/util/Locale.java

@@ -2886,11 +2886,11 @@
             }
             if (weight < MIN_WEIGHT || weight > MAX_WEIGHT) {
                 throw new IllegalArgumentException("weight=" + weight);
             }
 
-            range = range.toLowerCase();
+            range = range.toLowerCase(Locale.ROOT);
 
             // Do syntax check.
             boolean isIllFormed = false;
             String[] subtags = range.split("-");
             if (isSubtagIllFormed(subtags[0], true)