diff --git a/components/radio/group.tsx b/components/radio/group.tsx
index 7d54a712fb..931ec188cf 100644
--- a/components/radio/group.tsx
+++ b/components/radio/group.tsx
@@ -3,7 +3,7 @@ import PropTypes from 'prop-types';
 import classNames from 'classnames';
 import shallowEqual from 'shallowequal';
 import Radio from './radio';
-import { RadioGroupProps, RadioGroupState, RadioChangeEvent } from './interface';
+import { RadioGroupProps, RadioGroupState, RadioChangeEvent, RadioGroupButtonStyle } from './interface';
 
 function getCheckedValue(children: React.ReactNode) {
   let value = null;
@@ -21,7 +21,7 @@ export default class RadioGroup extends React.Component<RadioGroupProps, RadioGr
   static defaultProps = {
     disabled: false,
     prefixCls: 'ant-radio',
-    buttonStyle: 'outline',
+    buttonStyle: 'outline' as RadioGroupButtonStyle,
   };
 
   static childContextTypes = {
diff --git a/components/radio/interface.tsx b/components/radio/interface.tsx
index c83aba012f..40a72f871e 100644
--- a/components/radio/interface.tsx
+++ b/components/radio/interface.tsx
@@ -2,6 +2,8 @@ import * as React from 'react';
 import { AbstractCheckboxGroupProps } from '../checkbox/Group';
 import { AbstractCheckboxProps } from '../checkbox/Checkbox';
 
+export type RadioGroupButtonStyle = 'outline' | 'solid';
+
 export interface RadioGroupProps extends AbstractCheckboxGroupProps {
   defaultValue?: any;
   value?: any;
@@ -12,7 +14,7 @@ export interface RadioGroupProps extends AbstractCheckboxGroupProps {
   name?: string;
   children?: React.ReactNode;
   id?: string;
-  buttonStyle?: 'outline' | 'solid';
+  buttonStyle?: RadioGroupButtonStyle;
 }
 
 export interface RadioGroupState {