diff --git a/packages/core/client/src/schema-component/antd/upload/Upload.tsx b/packages/core/client/src/schema-component/antd/upload/Upload.tsx
index 728e1f70ad..6a1893ce3e 100644
--- a/packages/core/client/src/schema-component/antd/upload/Upload.tsx
+++ b/packages/core/client/src/schema-component/antd/upload/Upload.tsx
@@ -89,7 +89,7 @@ attachmentFileTypes.add({
   },
 });
 
-const iframePreviewSupportedTypes = ['application/pdf', 'audio/*', 'image/*', 'video/*', 'text/*'];
+const iframePreviewSupportedTypes = ['application/pdf', 'audio/*', 'image/*', 'video/*', 'text/plain'];
 
 function IframePreviewer({ index, list, onSwitchIndex }) {
   const { t } = useTranslation();