diff --git a/decls/i18n.js b/decls/i18n.js
index 6230b98fc..b22eb8ec4 100644
--- a/decls/i18n.js
+++ b/decls/i18n.js
@@ -33,6 +33,7 @@ declare interface I18n {
   set missing (handler: MissingHandler): void,
   get formatter (): Formatter,
   set formatter (formatter: Formatter): void,
+  setLocaleMessage (locale: Locale, message: LocaleMessage): void,
   t (key: Path, ...args: any): TranslateResult,
   tc (key: Path, choice?: number, ...args: any): TranslateResult,
   te (key: Path, ...args: any): boolean,
diff --git a/src/index.js b/src/index.js
index 6ce345cf2..051ff46f0 100644
--- a/src/index.js
+++ b/src/index.js
@@ -216,6 +216,10 @@ export default class VueI18n {
   te (key: Path, ...args: any): boolean {
     return this._te(key, this.locale, this.messages, ...args)
   }
+
+  setLocaleMessage (locale: Locale, message: LocaleMessage): void {
+    this._vm.messages[locale] = message
+  }
 }
 
 VueI18n.install = install
diff --git a/test/unit/hot.test.js b/test/unit/hot.test.js
index aa1e4a9dc..2bde514af 100644
--- a/test/unit/hot.test.js
+++ b/test/unit/hot.test.js
@@ -3,11 +3,18 @@ import messages from './fixture/index'
 describe('hot reloading', () => {
   let el
   let i18n
-  let orgLocale
-  const expectLocale = 'the world updated'
+  let orgEnLocale
+  let orgJaLocaleMessage
+  const expectEnLocale = 'the world updated'
+  const expectJaLocaleMessage = {
+    message: {
+      hello: 'ザ・世界 -> メイド・イン・ヘブン'
+    }
+  }
 
   beforeEach(() => {
-    orgLocale = messages.en.message.hello
+    orgEnLocale = messages.en.message.hello
+    orgJaLocaleMessage = messages.ja
     i18n = new VueI18n({
       locale: 'en',
       messages
@@ -18,7 +25,8 @@ describe('hot reloading', () => {
   })
 
   afterEach(() => {
-    messages.en.message.hello = orgLocale
+    messages.en.message.hello = orgEnLocale
+    messages.ja = orgJaLocaleMessage
     i18n.messages = messages
   })
 
@@ -34,10 +42,15 @@ describe('hot reloading', () => {
     waitForUpdate(() => {
       assert.equal(text.textContent, messages.en.message.hello)
       // hot reload (set reactivity messages)
-      messages.en.message.hello = expectLocale
+      messages.en.message.hello = expectEnLocale
       i18n.messages = messages
     }).then(() => {
-      assert.equal(text.textContent, expectLocale)
+      assert.equal(text.textContent, expectEnLocale)
+      // upade locale
+      i18n.setLocaleMessage('ja', expectJaLocaleMessage)
+      i18n.locale = 'ja'
+    }).then(() => {
+      assert.equal(text.textContent, expectJaLocaleMessage.message.hello)
     }).then(done)
   })
 })