diff --git a/web/components/button.react.js b/web/components/button.react.js
index 265553c9a..2f0ce303d 100644
--- a/web/components/button.react.js
+++ b/web/components/button.react.js
@@ -1,40 +1,40 @@
 // @flow
 
 import classnames from 'classnames';
 import * as React from 'react';
 
 import css from './button.css';
 
 type Props = {
-  +onClick: (event: SyntheticEvent<HTMLButtonElement>) => void,
+  +onClick: (event: SyntheticEvent<HTMLButtonElement>) => mixed,
   +children: React.Node,
   +variant?: 'primary' | 'secondary' | 'danger' | 'round',
   +type?: string,
   +disabled?: boolean,
   +className?: string,
 };
 
 function Button(props: Props): React.Node {
   const {
     onClick,
     children,
     variant = 'primary',
     type,
     disabled = false,
     className = '',
   } = props;
   const btnCls = classnames(css.btn, css[variant]);
 
   return (
     <button
       type={type}
       className={`${btnCls} ${className}`}
       onClick={onClick}
       disabled={disabled}
     >
       {children}
     </button>
   );
 }
 
 export default Button;