diff --git a/src/plugin/relativeTime/index.js b/src/plugin/relativeTime/index.js
index 022fbfbd8..e11b67a8e 100644
--- a/src/plugin/relativeTime/index.js
+++ b/src/plugin/relativeTime/index.js
@@ -60,7 +60,11 @@ export default (o, c, d) => {
       }
     }
     if (withoutSuffix) return out
-    return (isFuture ? loc.future : loc.past).replace('%s', out)
+    const pastOrFuture = isFuture ? loc.future : loc.past
+    if (typeof pastOrFuture === 'function') {
+      return pastOrFuture(out)
+    }
+    return pastOrFuture.replace('%s', out)
   }
   proto.to = function (input, withoutSuffix) {
     return fromTo(input, withoutSuffix, this, true)
diff --git a/test/plugin/relativeTime.test.js b/test/plugin/relativeTime.test.js
index 19994381f..0ef8e796a 100644
--- a/test/plugin/relativeTime.test.js
+++ b/test/plugin/relativeTime.test.js
@@ -3,6 +3,7 @@ import moment from 'moment'
 import dayjs from '../../src'
 import * as C from '../../src/constant'
 import relativeTime from '../../src/plugin/relativeTime'
+import updateLocale from '../../src/plugin/updateLocale'
 import utc from '../../src/plugin/utc'
 import '../../src/locale/ru'
 
@@ -143,3 +144,30 @@ it('Locale without relativeTime config fallback', () => {
     name: 'test-locale'
   }).fromNow()).toEqual(expect.any(String))
 })
+
+it('Past and Future keys should support function for additional processing', () => {
+  dayjs.extend(updateLocale)
+  dayjs.updateLocale('en', {
+    relativeTime: {
+      future: input => `${input} modified`,
+      past: input => `${input} modified`,
+      s: 'just now',
+      m: ' 1 min',
+      mm: '%d min',
+      h: '1 hr',
+      hh: '%d hrs',
+      d: 'a day',
+      dd: '%d days',
+      M: 'a month',
+      MM: '%d months',
+      y: 'a year',
+      yy: '%d years'
+    }
+  })
+
+
+  const past = Date.now() - 1000
+  expect(dayjs(past).fromNow()).toEqual(' 1 min modified')
+  const future = Date.now() + 1000
+  expect(dayjs(future).fromNow()).toEqual(' 1 min modified')
+})