diff --git a/spring-context/src/main/java/org/springframework/validation/DataBinder.java b/spring-context/src/main/java/org/springframework/validation/DataBinder.java
index c2e5ecfa3b07..3d1902f40e3b 100644
--- a/spring-context/src/main/java/org/springframework/validation/DataBinder.java
+++ b/spring-context/src/main/java/org/springframework/validation/DataBinder.java
@@ -23,6 +23,7 @@
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 
 import org.apache.commons.logging.Log;
@@ -482,7 +483,8 @@ public void setDisallowedFields(@Nullable String... disallowedFields) {
 		else {
 			String[] fieldPatterns = new String[disallowedFields.length];
 			for (int i = 0; i < fieldPatterns.length; i++) {
-				fieldPatterns[i] = PropertyAccessorUtils.canonicalPropertyName(disallowedFields[i]).toLowerCase();
+				String field = PropertyAccessorUtils.canonicalPropertyName(disallowedFields[i]);
+				fieldPatterns[i] = field.toLowerCase(Locale.ROOT);
 			}
 			this.disallowedFields = fieldPatterns;
 		}
@@ -825,7 +827,7 @@ protected boolean isAllowed(String field) {
 		String[] allowed = getAllowedFields();
 		String[] disallowed = getDisallowedFields();
 		return ((ObjectUtils.isEmpty(allowed) || PatternMatchUtils.simpleMatch(allowed, field)) &&
-				(ObjectUtils.isEmpty(disallowed) || !PatternMatchUtils.simpleMatch(disallowed, field.toLowerCase())));
+				(ObjectUtils.isEmpty(disallowed) || !PatternMatchUtils.simpleMatch(disallowed, field.toLowerCase(Locale.ROOT))));
 	}
 
 	/**