diff --git a/examples/with-stitches-styled/pages/_document.js b/examples/with-stitches-styled/pages/_document.js
index df3b228357357..1cb439e124edb 100644
--- a/examples/with-stitches-styled/pages/_document.js
+++ b/examples/with-stitches-styled/pages/_document.js
@@ -20,8 +20,8 @@ export default class MyDocument extends Document {
         styles: (
           <>
             {initialProps.styles}
-            {extractedStyles.map((content) => (
-              <style>{content}</style>
+            {extractedStyles.map((content, index) => (
+              <style key={index}>{content}</style>
             ))}
           </>
         ),