diff --git a/subprojects/groovy-json/src/main/java/org/apache/groovy/json/internal/CharSequenceValue.java b/subprojects/groovy-json/src/main/java/org/apache/groovy/json/internal/CharSequenceValue.java
index facea9a6e47..de8491fe665 100644
--- a/subprojects/groovy-json/src/main/java/org/apache/groovy/json/internal/CharSequenceValue.java
+++ b/subprojects/groovy-json/src/main/java/org/apache/groovy/json/internal/CharSequenceValue.java
@@ -24,6 +24,7 @@
 import java.math.BigInteger;
 import java.util.Arrays;
 import java.util.Date;
+import java.util.Locale;
 import java.util.Objects;
 
 import static org.apache.groovy.json.internal.CharScanner.isInteger;
@@ -131,7 +132,7 @@ public static <T extends Enum> T toEnum(Class<T> cls, String value) {
         try {
             return (T) Enum.valueOf(cls, value);
         } catch (Exception ex) {
-            return (T) Enum.valueOf(cls, value.toUpperCase().replace('-', '_'));
+            return (T) Enum.valueOf(cls, value.toUpperCase(Locale.ROOT).replace('-', '_'));
         }
     }