diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactory.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactory.java
index 0929ece547..ff31364eb2 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactory.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactory.java
@@ -266,6 +266,7 @@ public class TomcatServletWebServerFactory extends AbstractServletWebServerFacto
 	private void resetDefaultLocaleMapping(TomcatEmbeddedContext context) {
 		context.addLocaleEncodingMappingParameter(Locale.ENGLISH.toString(), DEFAULT_CHARSET.displayName());
 		context.addLocaleEncodingMappingParameter(Locale.FRENCH.toString(), DEFAULT_CHARSET.displayName());
+		context.addLocaleEncodingMappingParameter(Locale.JAPANESE.toString(), DEFAULT_CHARSET.displayName());
 	}
 
 	private void addLocaleMappings(TomcatEmbeddedContext context) {
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactoryTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactoryTests.java
index cbf256e7ae..d467117edc 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactoryTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactoryTests.java
@@ -410,6 +410,7 @@ class TomcatServletWebServerFactoryTests extends AbstractServletWebServerFactory
 		// override defaults, see org.apache.catalina.util.CharsetMapperDefault.properties
 		assertThat(getCharset(Locale.ENGLISH)).isEqualTo(StandardCharsets.UTF_8);
 		assertThat(getCharset(Locale.FRENCH)).isEqualTo(StandardCharsets.UTF_8);
+		assertThat(getCharset(Locale.JAPANESE)).isEqualTo(StandardCharsets.UTF_8);
 	}
 
 	@Test