diff --git a/spring-web/src/test/java/org/springframework/web/bind/MethodArgumentNotValidExceptionTests.java b/spring-web/src/test/java/org/springframework/web/bind/MethodArgumentNotValidExceptionTests.java
index 4c05b784dca..3d71f1f133d 100644
--- a/spring-web/src/test/java/org/springframework/web/bind/MethodArgumentNotValidExceptionTests.java
+++ b/spring-web/src/test/java/org/springframework/web/bind/MethodArgumentNotValidExceptionTests.java
@@ -24,6 +24,7 @@ import jakarta.validation.constraints.Min;
 import jakarta.validation.constraints.Size;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.context.support.StaticMessageSource;
 import org.springframework.core.MethodParameter;
 import org.springframework.validation.BeanPropertyBindingResult;
@@ -36,6 +37,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Unit tests for {@link MethodArgumentNotValidException}.
+ *
  * @author Rossen Stoyanchev
  */
 public class MethodArgumentNotValidExceptionTests {
@@ -68,17 +70,23 @@ public class MethodArgumentNotValidExceptionTests {
 	}
 
 	private static MethodArgumentNotValidException createException(Person person) throws Exception {
-		LocalValidatorFactoryBean validatorBean = new LocalValidatorFactoryBean();
-		validatorBean.afterPropertiesSet();
-		SpringValidatorAdapter validator = new SpringValidatorAdapter(validatorBean);
+		LocaleContextHolder.setLocale(Locale.UK);
+		try {
+			LocalValidatorFactoryBean validatorBean = new LocalValidatorFactoryBean();
+			validatorBean.afterPropertiesSet();
+			SpringValidatorAdapter validator = new SpringValidatorAdapter(validatorBean);
 
-		BindingResult result = new BeanPropertyBindingResult(person, "person");
-		validator.validate(person, result);
+			BindingResult result = new BeanPropertyBindingResult(person, "person");
+			validator.validate(person, result);
 
-		Method method = Handler.class.getDeclaredMethod("handle", Person.class);
-		MethodParameter parameter = new MethodParameter(method, 0);
+			Method method = Handler.class.getDeclaredMethod("handle", Person.class);
+			MethodParameter parameter = new MethodParameter(method, 0);
 
-		return new MethodArgumentNotValidException(parameter, result);
+			return new MethodArgumentNotValidException(parameter, result);
+		}
+		finally {
+			LocaleContextHolder.resetLocaleContext();
+		}
 	}
 
 
diff --git a/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MethodValidationTests.java b/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MethodValidationTests.java
index 704bbe1cb2b..619a3e759cb 100644
--- a/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MethodValidationTests.java
+++ b/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MethodValidationTests.java
@@ -19,6 +19,7 @@ package org.springframework.web.reactive.result.method.annotation;
 import java.lang.reflect.Method;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Set;
 import java.util.function.Consumer;
 
@@ -27,12 +28,14 @@ import jakarta.validation.Valid;
 import jakarta.validation.constraints.Size;
 import jakarta.validation.executable.ExecutableValidator;
 import jakarta.validation.metadata.BeanDescriptor;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
 import org.springframework.context.MessageSourceResolvable;
+import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.validation.Errors;
@@ -63,12 +66,14 @@ import static org.mockito.Mockito.mock;
 
 /**
  * Method validation tests for Spring MVC controller methods.
+ *
  * <p>When adding tests, consider the following others:
  * <ul>
  * <li>{@code HandlerMethodTests} -- detection if methods need validation
  * <li>{@code MethodValidationAdapterTests} -- method validation independent of Spring MVC
  * <li>{@code MethodValidationProxyTests} -- method validation with proxy scenarios
  * </ul>
+ *
  * @author Rossen Stoyanchev
  */
 public class MethodValidationTests {
@@ -85,6 +90,8 @@ public class MethodValidationTests {
 
 	@BeforeEach
 	void setup() throws Exception {
+		LocaleContextHolder.setDefaultLocale(Locale.UK);
+
 		LocalValidatorFactoryBean validatorBean = new LocalValidatorFactoryBean();
 		validatorBean.afterPropertiesSet();
 		this.jakartaValidator = new InvocationCountingValidator(validatorBean);
@@ -105,6 +112,11 @@ public class MethodValidationTests {
 		return handlerAdapter;
 	}
 
+	@AfterEach
+	void reset() {
+		LocaleContextHolder.setDefaultLocale(null);
+	}
+
 
 	@Test
 	void modelAttribute() {