diff --git a/src/components/ToolBar/index.tsx b/src/components/ToolBar/index.tsx
index cdceeda2..32c5e603 100644
--- a/src/components/ToolBar/index.tsx
+++ b/src/components/ToolBar/index.tsx
@@ -24,7 +24,7 @@ export default class ToolBar extends React.PureComponent<IToolBarProps, {}> {
         {toolbars.map((name: string, key) => {
           const Icon = (icon as unknown as IIconProps)[name];
           return (
-            <button key={key} onClick={onClick.bind(this, name)}> {Icon} </button>
+            <button type="button" key={key} onClick={onClick.bind(this, name)}> {Icon} </button>
           );
         })}
       </div>
diff --git a/src/components/ToolBarMode/index.tsx b/src/components/ToolBarMode/index.tsx
index b934d7e0..25de1502 100644
--- a/src/components/ToolBarMode/index.tsx
+++ b/src/components/ToolBarMode/index.tsx
@@ -46,6 +46,7 @@ export default class ToolBarMode extends React.PureComponent<IToolBarModeProps,
           return (
             <button
               key={key}
+              type="button"
               className={classnames({
                 active: (preview && name === 'preview') || fullscreen && name === 'fullscreen',
               })}