diff --git a/app/soapbox/features/ui/util/pending_status_builder.js b/app/soapbox/features/ui/util/pending_status_builder.js
index 552e7e7ac..433436d56 100644
--- a/app/soapbox/features/ui/util/pending_status_builder.js
+++ b/app/soapbox/features/ui/util/pending_status_builder.js
@@ -42,7 +42,7 @@ export const buildStatus = (state, pendingStatus, idempotencyKey) => {
     in_reply_to_account_id: null,
     in_reply_to_id: pendingStatus.get('in_reply_to_id'),
     language: null,
-    media_attachments: pendingStatus.get('media_ids').map(id => ({ id })),
+    media_attachments: pendingStatus.get('media_ids').map(id => (ImmutableMap({ id }))),
     mentions,
     muted: false,
     pinned: false,