diff --git a/packages/next-plugin-storybook/preset.js b/packages/next-plugin-storybook/preset.js
index 57f3605ea321b..12ccb983e6063 100644
--- a/packages/next-plugin-storybook/preset.js
+++ b/packages/next-plugin-storybook/preset.js
@@ -28,7 +28,7 @@ async function webpackFinal(config) {
   config.module.rules = [
     ...config.module.rules.filter((rule) => {
       // the rules we're filtering use RegExp for the test
-      if (!rule.test instanceof RegExp) return true
+      if (!(rule.test instanceof RegExp)) return true
       // use Next.js' built-in CSS
       if (rule.test.test('hello.css')) {
         return false