diff --git a/apps/knowledge/serializers/document.py b/apps/knowledge/serializers/document.py
index dd85f178..304ea40d 100644
--- a/apps/knowledge/serializers/document.py
+++ b/apps/knowledge/serializers/document.py
@@ -563,7 +563,7 @@ class DocumentSerializers(serializers.Serializer):
             self.is_valid(raise_exception=True)
             file = QuerySet(File).filter(source_id=self.data.get('document_id')).first()
             if not file:
-                raise AppApiException(500, _('file not exist'))
+                raise AppApiException(500, _('File not exist. Only manually uploaded documents are supported.'))
             return FileSerializer.Operate(data={'id': file.id}).get(with_valid=True)
 
         def one(self, with_valid=False):