diff --git a/src/format.js b/src/format.js
index 9c461731b..79b92fb4b 100644
--- a/src/format.js
+++ b/src/format.js
@@ -13,7 +13,7 @@ export default class BaseFormatter {
 
   get options (): FormatterOptions { return this._options }
 
-  format (message: string, values: any): any {
+  interpolate (message: string, values: any): Array<any> {
     let tokens: Array<Token> = this._caches[message]
     if (!tokens) {
       tokens = parse(message)
diff --git a/src/index.js b/src/index.js
index 0fd28470d..f0af88b07 100644
--- a/src/index.js
+++ b/src/index.js
@@ -220,7 +220,7 @@ export default class VueI18n {
   }
 
   _render (message: string, interpolateMode: string, values: any): any {
-    const ret = this._formatter.format(message, values)
+    const ret = this._formatter.interpolate(message, values)
     // if interpolateMode is **not** 'string' ('row'),
     // return the compiled data (e.g. ['foo', VNode, 'bar']) with formatter
     return interpolateMode === 'string' ? ret.join('') : ret
diff --git a/test/unit/format_custom.test.js b/test/unit/format_custom.test.js
index b1bc42a3f..949f2d26c 100644
--- a/test/unit/format_custom.test.js
+++ b/test/unit/format_custom.test.js
@@ -4,8 +4,8 @@ describe('custom formatter', () => {
   describe('via i18n instance API calling', () => {
     it('should allows for specifying a custom formatter', done => {
       class CustomFormatter {
-        format (message, ...args) {
-          assert.deepEqual({ name: 'joe' }, args[0])
+        interpolate (message, values) {
+          assert.deepEqual({ name: 'joe' }, values)
           done()
         }
       }
@@ -22,8 +22,8 @@ describe('custom formatter', () => {
   describe('via vue instance calling', () => {
     it('should allows for specifying a custom formatter', done => {
       const formatter = {
-        format: (message, ...args) => {
-          assert.deepEqual([1, 2, 3], args[0])
+        interpolate: (message, values) => {
+          assert.deepEqual([1, 2, 3], values)
           done()
         }
       }