diff --git a/packages/react-dom-bindings/src/client/ReactDOMComponent.js b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
index 6e7b2da23ecc1..5aad853a76059 100644
--- a/packages/react-dom-bindings/src/client/ReactDOMComponent.js
+++ b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
@@ -2211,7 +2211,7 @@ function diffHydratedCustomComponent(
         continue;
 
       // Fall through
-      case 'className':
+      case 'className': {
         // className is a special cased property on the server to render as an attribute.
         extraAttributes.delete('class');
         const serverValue = getValueForAttributeOnCustomComponent(
@@ -2221,6 +2221,7 @@ function diffHydratedCustomComponent(
         );
         warnForPropDifference('className', serverValue, value);
         continue;
+      }
 
       // Fall through
       default: {