diff --git a/packages/backend/src/server/api/mastodon/converters.ts b/packages/backend/src/server/api/mastodon/converters.ts
index 038319139..8fc7dd001 100644
--- a/packages/backend/src/server/api/mastodon/converters.ts
+++ b/packages/backend/src/server/api/mastodon/converters.ts
@@ -272,7 +272,7 @@ export class MastoConverters {
 			poll: status.poll ?? null,
 			application: null, //FIXME
 			language: null, //FIXME
-			pinned: null,
+			pinned: false,
 			reactions: status.emoji_reactions,
 			emoji_reactions: status.emoji_reactions,
 			bookmarked: false,