diff --git a/electron/servers/fastapi/api/v1/ppt/endpoints/presentation.py b/electron/servers/fastapi/api/v1/ppt/endpoints/presentation.py
index ec147dce..a26eaa57 100644
--- a/electron/servers/fastapi/api/v1/ppt/endpoints/presentation.py
+++ b/electron/servers/fastapi/api/v1/ppt/endpoints/presentation.py
@@ -407,7 +407,7 @@ async def update_presentation(
         presentation_update_dict["n_slides"] = n_slides
     if title:
         presentation_update_dict["title"] = title
-    if theme:
+    if theme or theme is None:
         presentation_update_dict["theme"] = theme
 
     if presentation_update_dict: