diff --git a/spring-web/src/main/java/org/springframework/web/ErrorResponse.java b/spring-web/src/main/java/org/springframework/web/ErrorResponse.java
index dfc545bb2da..c83bcdb1c4b 100644
--- a/spring-web/src/main/java/org/springframework/web/ErrorResponse.java
+++ b/spring-web/src/main/java/org/springframework/web/ErrorResponse.java
@@ -40,7 +40,6 @@ import org.springframework.lang.Nullable;
  * {@code @RestController} or {@code RestControllerAdvice} class.
  *
  * @author Rossen Stoyanchev
- * @author Yanming Zhou
  * @since 6.0
  * @see ErrorResponseException
  */
@@ -143,14 +142,6 @@ public interface ErrorResponse {
 			if (detail != null) {
 				getBody().setDetail(detail);
 			}
-			else {
-				// detail from ResponseStatusException reason may be message code
-				detail = getBody().getDetail();
-				if (detail != null) {
-					detail = messageSource.getMessage(detail, null, detail, locale);
-					getBody().setDetail(detail);
-				}
-			}
 			String title = messageSource.getMessage(getTitleMessageCode(), null, null, locale);
 			if (title != null) {
 				getBody().setTitle(title);
diff --git a/spring-web/src/main/java/org/springframework/web/server/ResponseStatusException.java b/spring-web/src/main/java/org/springframework/web/server/ResponseStatusException.java
index c779133e5e6..8e9c039aae7 100644
--- a/spring-web/src/main/java/org/springframework/web/server/ResponseStatusException.java
+++ b/spring-web/src/main/java/org/springframework/web/server/ResponseStatusException.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,9 @@
 
 package org.springframework.web.server;
 
+import java.util.Locale;
+
+import org.springframework.context.MessageSource;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatusCode;
 import org.springframework.http.ProblemDetail;
@@ -127,6 +130,23 @@ public class ResponseStatusException extends ErrorResponseException {
 		return HttpHeaders.EMPTY;
 	}
 
+	@Override
+	public ProblemDetail updateAndGetBody(@Nullable MessageSource messageSource, Locale locale) {
+		super.updateAndGetBody(messageSource, locale);
+
+		// The reason may be a code (consistent with ResponseStatusExceptionResolver)
+
+		if (messageSource != null && getReason() != null && getReason().equals(getBody().getDetail())) {
+			Object[] arguments = getDetailMessageArguments(messageSource, locale);
+			String resolved = messageSource.getMessage(getReason(), arguments, null, locale);
+			if (resolved != null) {
+				getBody().setDetail(resolved);
+			}
+		}
+
+		return getBody();
+	}
+
 	@Override
 	public String getMessage() {
 		return getStatusCode() + (this.reason != null ? " \"" + this.reason + "\"" : "");
diff --git a/spring-web/src/test/java/org/springframework/web/ErrorResponseExceptionTests.java b/spring-web/src/test/java/org/springframework/web/ErrorResponseExceptionTests.java
index 1427aa964b0..6405a092cd1 100644
--- a/spring-web/src/test/java/org/springframework/web/ErrorResponseExceptionTests.java
+++ b/spring-web/src/test/java/org/springframework/web/ErrorResponseExceptionTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,7 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.testfixture.beans.TestBean;
 import org.springframework.context.MessageSourceResolvable;
+import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.context.support.StaticMessageSource;
 import org.springframework.core.MethodParameter;
 import org.springframework.http.HttpHeaders;
@@ -51,6 +52,7 @@ import org.springframework.web.multipart.support.MissingServletRequestPartExcept
 import org.springframework.web.server.MethodNotAllowedException;
 import org.springframework.web.server.MissingRequestValueException;
 import org.springframework.web.server.NotAcceptableStatusException;
+import org.springframework.web.server.ResponseStatusException;
 import org.springframework.web.server.ServerErrorException;
 import org.springframework.web.server.UnsatisfiedRequestParameterException;
 import org.springframework.web.server.UnsupportedMediaTypeStatusException;
@@ -415,6 +417,28 @@ public class ErrorResponseExceptionTests {
 		assertThat(ex.getHeaders()).isEmpty();
 	}
 
+	@Test // gh-30300
+	void responseStatusException() {
+
+		Locale locale = Locale.UK;
+		LocaleContextHolder.setLocale(locale);
+
+		try {
+			String reason = "bad.request";
+			String message = "Breaking Bad Request";
+			StaticMessageSource messageSource = new StaticMessageSource();
+			messageSource.addMessage(reason, locale, message);
+
+			ResponseStatusException ex = new ResponseStatusException(HttpStatus.BAD_REQUEST, reason);
+
+			ProblemDetail problemDetail = ex.updateAndGetBody(messageSource, locale);
+			assertThat(problemDetail.getDetail()).isEqualTo(message);
+		}
+		finally {
+			LocaleContextHolder.resetLocaleContext();
+		}
+	}
+
 	private void assertStatus(ErrorResponse ex, HttpStatus status) {
 		ProblemDetail body = ex.getBody();
 		assertThat(ex.getStatusCode()).isEqualTo(status);
diff --git a/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseEntityExceptionHandlerTests.java b/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseEntityExceptionHandlerTests.java
index bee3c569e40..94dcc038e72 100644
--- a/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseEntityExceptionHandlerTests.java
+++ b/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseEntityExceptionHandlerTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -201,21 +201,21 @@ public class ResponseEntityExceptionHandlerTests {
 		}
 	}
 
-	@Test
+	@Test // gh-30300
 	public void reasonAsDetailShouldBeUpdatedViaMessageSource() {
 
 		Locale locale = Locale.UK;
 		LocaleContextHolder.setLocale(locale);
 
-		String code = "bad.request";
+		String reason = "bad.request";
 		String message = "Breaking Bad Request";
 		try {
 			StaticMessageSource messageSource = new StaticMessageSource();
-			messageSource.addMessage(code, locale, message);
+			messageSource.addMessage(reason, locale, message);
 
 			this.exceptionHandler.setMessageSource(messageSource);
 
-			ResponseEntity<?> entity = testException(new ResponseStatusException(HttpStatus.BAD_REQUEST, code));
+			ResponseEntity<?> entity = testException(new ResponseStatusException(HttpStatus.BAD_REQUEST, reason));
 
 			ProblemDetail body = (ProblemDetail) entity.getBody();
 			assertThat(body.getDetail()).isEqualTo(message);