diff --git a/.changeset/vast-jeans-boil.md b/.changeset/vast-jeans-boil.md
index 74b2c481b4..7fbc49cdfa 100644
--- a/.changeset/vast-jeans-boil.md
+++ b/.changeset/vast-jeans-boil.md
@@ -10,7 +10,7 @@ This addresses the problem where the elements contain the `v5-` prefix for MUI c
 Import should be made as follows to ensure the prefix problem is addressed correctly:
 
 ```diff
-// packages/app/src/index.ts
+// packages/app/src/index.tsx
 
 + import '@backstage/theme/MuiClassNameSetup'; // must be the very first import!
 import '@backstage/cli/asset-types';
diff --git a/packages/theme/src/unified/MuiClassNameSetup.ts b/packages/theme/src/unified/MuiClassNameSetup.ts
index 9511376f5a..b069394838 100644
--- a/packages/theme/src/unified/MuiClassNameSetup.ts
+++ b/packages/theme/src/unified/MuiClassNameSetup.ts
@@ -21,7 +21,7 @@ import { unstable_ClassNameGenerator as ClassNameGenerator } from '@mui/material
  * This needs to be configured before any MUI 5 component can possibly be imported. See: https://v5.mui.com/material-ui/experimental-api/classname-generator/#caveat
  *
  * ```diff
- * // packages/app/src/index.ts
+ * // packages/app/src/index.tsx
  *
  * + import '@backstage/theme/MuiClassNameSetup'; // must be the very first import!
  * import '@backstage/cli/asset-types';