diff --git a/packages/netlify-cms-core/src/redux/index.js b/packages/netlify-cms-core/src/redux/index.js
index d3076d1f..720b8011 100644
--- a/packages/netlify-cms-core/src/redux/index.js
+++ b/packages/netlify-cms-core/src/redux/index.js
@@ -7,7 +7,7 @@ const store = createStore(
   reducer,
   compose(
     applyMiddleware(thunkMiddleware, waitUntilAction),
-    window.devToolsExtension ? window.devToolsExtension() : f => f,
+    window.__REDUX_DEVTOOLS_EXTENSION__ ? window.__REDUX_DEVTOOLS_EXTENSION__() : f => f,
   ),
 );
 
diff --git a/packages/netlify-cms-widget-markdown/src/MarkdownControl/Toolbar.js b/packages/netlify-cms-widget-markdown/src/MarkdownControl/Toolbar.js
index b5a86bbc..7e7891c9 100644
--- a/packages/netlify-cms-widget-markdown/src/MarkdownControl/Toolbar.js
+++ b/packages/netlify-cms-widget-markdown/src/MarkdownControl/Toolbar.js
@@ -175,7 +175,7 @@ export default class Toolbar extends React.Component {
                         <DropdownItem
                           key={idx}
                           label={headingOptions[optionKey]}
-                          className={selectionHasBlock(optionKey) && 'active'}
+                          className={selectionHasBlock(optionKey) ? 'active' : undefined}
                           onClick={() => onBlockClick(undefined, optionKey)}
                         />
                       ),