diff --git a/backend/app/core/doctransform/service.py b/backend/app/core/doctransform/service.py
index 2e3f2792..e119492f 100644
--- a/backend/app/core/doctransform/service.py
+++ b/backend/app/core/doctransform/service.py
@@ -89,11 +89,7 @@ def execute_job(
         convert_document(tmp_in, tmp_out, transformer_name)
 
         # Determine content type based on target format
-        content_type_map = {
-            "markdown": "text/markdown",
-            "text": "text/plain",
-            "html": "text/html",
-        }
+        content_type_map = {"markdown": "text/markdown; charset=utf-8"}
         content_type = content_type_map.get(target_format, "text/plain")
 
         # upload transformed file and create document record