diff --git a/src/index.js b/src/index.js
index 9c4b93c12..8d0863559 100644
--- a/src/index.js
+++ b/src/index.js
@@ -24,8 +24,8 @@ const parseLocale = (preset, object, isLocal) => {
     Ls[name] = preset
     l = name
   }
-  if (!isLocal) L = l
-  return l
+  if (!isLocal && l) L = l
+  return l || (!isLocal && L)
 }
 
 const dayjs = (date, c, pl) => {
diff --git a/test/locale.test.js b/test/locale.test.js
index 48e1f5666..7faab1d08 100644
--- a/test/locale.test.js
+++ b/test/locale.test.js
@@ -12,6 +12,7 @@ afterEach(() => {
 })
 
 const format = 'dddd D, MMMM'
+const NOT_SUPPORTED_LOCALE_STRING = 'not_supported_locale_string'
 
 it('Uses spanish locale through constructor', () => { // not recommend
   expect(dayjs('2018-4-28', { locale: es })
@@ -123,10 +124,24 @@ describe('Instance locale inheritance', () => {
 })
 
 
-it('Not supported locale string fallback to previous one', () => {
+it('Not supported locale string fallback to previous one (instance)', () => {
   const D = dayjs()
-  const DFormat = D.format()
-  const D2 = D.locale('not_supported_locale_string')
-  const D2Format = D2.format()
-  expect(DFormat).toBe(D2Format)
+  expect(D.locale()).toBe('en')
+  const D2 = D.locale(NOT_SUPPORTED_LOCALE_STRING)
+  expect(D2.locale()).toBe('en')
+  expect(D2.format()).toBe(D.format())
+  const D3 = D2.locale('es')
+  expect(D3.locale()).toBe('es')
+  const D4 = D3.locale(NOT_SUPPORTED_LOCALE_STRING)
+  expect(D4.locale()).toBe('es')
+})
+
+it('Not supported locale string fallback to previous one (global)', () => {
+  expect(dayjs().locale()).toBe('en')
+  dayjs.locale(NOT_SUPPORTED_LOCALE_STRING)
+  expect(dayjs().locale()).toBe('en')
+  dayjs.locale('es')
+  expect(dayjs().locale()).toBe('es')
+  dayjs.locale(NOT_SUPPORTED_LOCALE_STRING)
+  expect(dayjs().locale()).toBe('es')
 })