diff --git a/src/client/components/sample.vue b/src/client/components/sample.vue
index 8fd79ceec9..0f29fc69bb 100644
--- a/src/client/components/sample.vue
+++ b/src/client/components/sample.vue
@@ -51,7 +51,7 @@ export default defineComponent({
 			text: '',
 			flag: true,
 			radio: 'misskey',
-			mfm: `Hello world! This is an @example mention. BTW you are @${this.$i.username}.\nAlso, here is ${config.url} and [example link](${config.url}). for more details, see https://example.com.\nAs you know #misskey is open-source software.`
+			mfm: `Hello world! This is an @example mention. BTW you are @${this.$i ? this.$i.username : 'guest'}.\nAlso, here is ${config.url} and [example link](${config.url}). for more details, see https://example.com.\nAs you know #misskey is open-source software.`
 		}
 	},