diff --git a/src/index.js b/src/index.js
index ebfad14..001f9ec 100644
--- a/src/index.js
+++ b/src/index.js
@@ -305,7 +305,7 @@ class Dayjs {
       M: $M + 1,
       MM: Utils.s($M + 1, 2, '0'),
       MMM: getShort(locale.monthsShort, $M, months, 3),
-      MMMM: months[$M] || months(this, str),
+      MMMM: getShort(months, $M),
       D: this.$D,
       DD: Utils.s(this.$D, 2, '0'),
       d: String(this.$W),
diff --git a/src/locale/ru.js b/src/locale/ru.js
index 8a6533b..225cd69 100644
--- a/src/locale/ru.js
+++ b/src/locale/ru.js
@@ -27,24 +27,31 @@ function relativeTimeWithPlural(number, withoutSuffix, key) {
 
   return `${number} ${plural(format[key], +number)}`
 }
+const months = (dayjsInstance, format) => {
+  if (MONTHS_IN_FORMAT.test(format)) {
+    return monthFormat[dayjsInstance.month()]
+  }
+  return monthStandalone[dayjsInstance.month()]
+}
+months.s = monthStandalone
+months.f = monthFormat
+
+const monthsShort = (dayjsInstance, format) => {
+  if (MONTHS_IN_FORMAT.test(format)) {
+    return monthShortFormat[dayjsInstance.month()]
+  }
+  return monthShortStandalone[dayjsInstance.month()]
+}
+monthsShort.s = monthShortStandalone
+monthsShort.f = monthShortFormat
 
 const locale = {
   name: 'ru',
   weekdays: 'воскресенье_понедельник_вторник_среда_четверг_пятница_суббота'.split('_'),
   weekdaysShort: 'вск_пнд_втр_срд_чтв_птн_сбт'.split('_'),
   weekdaysMin: 'вс_пн_вт_ср_чт_пт_сб'.split('_'),
-  months: (dayjsInstance, format) => {
-    if (MONTHS_IN_FORMAT.test(format)) {
-      return monthFormat[dayjsInstance.month()]
-    }
-    return monthStandalone[dayjsInstance.month()]
-  },
-  monthsShort: (dayjsInstance, format) => {
-    if (MONTHS_IN_FORMAT.test(format)) {
-      return monthShortFormat[dayjsInstance.month()]
-    }
-    return monthShortStandalone[dayjsInstance.month()]
-  },
+  months,
+  monthsShort,
   weekStart: 1,
   formats: {
     LT: 'H:mm',
diff --git a/src/plugin/customParseFormat/index.js b/src/plugin/customParseFormat/index.js
index 5077a14..b8426e7 100644
--- a/src/plugin/customParseFormat/index.js
+++ b/src/plugin/customParseFormat/index.js
@@ -9,7 +9,7 @@ const matchUpperCaseAMPM = /[AP]M/
 const matchLowerCaseAMPM = /[ap]m/
 const matchSigned = /[+-]?\d+/ // -inf - inf
 const matchOffset = /[+-]\d\d:?\d\d/ // +00:00 -00:00 +0000 or -0000
-const matchWord = /\d*[^\s\d-:/.()]+/ // Word
+const matchWord = /\d*[^\s\d-:/()]+/ // Word
 
 let locale
 
@@ -30,6 +30,13 @@ const zoneExpressions = [matchOffset, function (input) {
   zone.offset = offsetFromString(input)
 }]
 
+const getLocalePart = (name) => {
+  const part = locale[name]
+  return part && (
+    part.indexOf ? part : part.s.concat(part.f)
+  )
+}
+
 const expressions = {
   A: [matchUpperCaseAMPM, function (input) {
     this.afternoon = input === 'PM'
@@ -69,22 +76,21 @@ const expressions = {
   M: [match1to2, addInput('month')],
   MM: [match2, addInput('month')],
   MMM: [matchWord, function (input) {
-    const { months, monthsShort } = locale
-    const matchIndex = monthsShort
-      ? monthsShort.findIndex(month => month === input)
-      : months.findIndex(month => month.substr(0, 3) === input)
+    const months = getLocalePart('months')
+    const monthsShort = getLocalePart('monthsShort')
+    const matchIndex = (monthsShort || months.map(_ => _.substr(0, 3))).indexOf(input)
     if (matchIndex < 0) {
       throw new Error()
     }
-    this.month = matchIndex + 1
+    this.month = (matchIndex + 1) % 12
   }],
   MMMM: [matchWord, function (input) {
-    const { months } = locale
+    const months = getLocalePart('months')
     const matchIndex = months.indexOf(input)
     if (matchIndex < 0) {
       throw new Error()
     }
-    this.month = matchIndex + 1
+    this.month = (matchIndex + 1) % 12
   }],
   Y: [matchSigned, addInput('year')],
   YY: [match2, function (input) {
diff --git a/src/plugin/localeData/index.js b/src/plugin/localeData/index.js
index b6da1ca..f478d5a 100644
--- a/src/plugin/localeData/index.js
+++ b/src/plugin/localeData/index.js
@@ -1,11 +1,11 @@
 export default (o, c, dayjs) => { // locale needed later
   const proto = c.prototype
+  const getLocalePart = part => (part && (part.indexOf ? part : part.s))
   const getShort = (ins, target, full, num) => {
     const locale = ins.name ? ins : ins.$locale()
-    if (!locale[target]) {
-      return locale[full].map(f => f.substr(0, num))
-    }
-    return locale[target]
+    const targetLocale = getLocalePart(locale[target])
+    const fullLocale = getLocalePart(locale[full])
+    return targetLocale || fullLocale.map(f => f.substr(0, num))
   }
   const getDayjsLocaleObject = () => dayjs.Ls[dayjs.locale()]
   const localeData = function () {
@@ -38,7 +38,7 @@ export default (o, c, dayjs) => { // locale needed later
     }
   }
 
-  dayjs.months = () => getDayjsLocaleObject().months
+  dayjs.months = () => getShort(getDayjsLocaleObject(), 'months')
 
   dayjs.monthsShort = () => getShort(getDayjsLocaleObject(), 'monthsShort', 'months', 3)
 
diff --git a/test/locale/keys.test.js b/test/locale/keys.test.js
index 5def001..876d6b3 100644
--- a/test/locale/keys.test.js
+++ b/test/locale/keys.test.js
@@ -45,6 +45,8 @@ Locale.forEach((locale) => {
       expect(months).toEqual(expect.any(Array))
     } else {
       expect(months(dayjs(), 'str')).toEqual(expect.any(String))
+      expect(months.f).toEqual(expect.any(Array))
+      expect(months.s).toEqual(expect.any(Array))
     }
     // monthsShort could be a function or array
     if (monthsShort) {
@@ -52,6 +54,8 @@ Locale.forEach((locale) => {
         expect(monthsShort).toEqual(expect.any(Array))
       } else {
         expect(monthsShort(dayjs(), 'str')).toEqual(expect.any(String))
+        expect(monthsShort.f).toEqual(expect.any(Array))
+        expect(monthsShort.s).toEqual(expect.any(Array))
       }
     }
     // function pass date return string or number or null
diff --git a/test/plugin/customParseFormat.test.js b/test/plugin/customParseFormat.test.js
index a326c68..b031e88 100644
--- a/test/plugin/customParseFormat.test.js
+++ b/test/plugin/customParseFormat.test.js
@@ -4,6 +4,7 @@ import dayjs from '../../src'
 import customParseFormat from '../../src/plugin/customParseFormat'
 import uk from '../../src/locale/uk'
 import '../../src/locale/zh-cn'
+import '../../src/locale/ru'
 
 dayjs.extend(customParseFormat)
 
@@ -233,6 +234,18 @@ it('correctly parse ordinal', () => {
     .toBe(momentCN.locale())
 })
 
+describe('month function locale', () => {
+  it('MMMM', () => {
+    const input = '08 мая 2020'
+    const format = 'DD MMMM YYYY'
+    expect(dayjs(input, format, 'ru').valueOf()).toBe(moment(input, format, 'ru').valueOf())
+  })
+  it('MMM', () => {
+    const input = '08 февр. 2020'
+    const format = 'DD MMM YYYY'
+    expect(dayjs(input, format, 'ru').valueOf()).toBe(moment(input, format, 'ru').valueOf())
+  })
+})
 
 describe('Strict mode', () => {
   it('without locale', () => {
diff --git a/test/plugin/localeData.test.js b/test/plugin/localeData.test.js
index 288c133..6dac0a9 100644
--- a/test/plugin/localeData.test.js
+++ b/test/plugin/localeData.test.js
@@ -5,6 +5,7 @@ import localeData from '../../src/plugin/localeData'
 import localizedFormat from '../../src/plugin/localizedFormat'
 import '../../src/locale/fr'
 import '../../src/locale/zh-cn'
+import '../../src/locale/ru'
 
 dayjs.extend(localizedFormat)
 dayjs.extend(localeData)
@@ -65,3 +66,14 @@ it('Listing the months and weekdays', () => {
     expect(dayjs.weekdaysMin()).toEqual(moment.weekdaysMin())
   })
 })
+
+it('Month function', () => {
+  const dayjsLocaleData = dayjs().locale('ru').localeData()
+  const momentLocaleData = moment().locale('ru').localeData()
+  expect(dayjsLocaleData.months()).toEqual(momentLocaleData.months())
+  expect(dayjsLocaleData.monthsShort()).toEqual(momentLocaleData.monthsShort())
+  dayjs.locale('ru')
+  moment.locale('ru')
+  expect(dayjs.months()).toEqual(moment.months())
+  expect(dayjs.monthsShort()).toEqual(moment.monthsShort())
+})