diff --git a/renderer/visualizer.py b/renderer/visualizer.py
index fbc8cb8..45edc2a 100644
--- a/renderer/visualizer.py
+++ b/renderer/visualizer.py
@@ -188,8 +188,9 @@ def _visualize_screenless_naive(self, meshList, skelList=None, body_bbox_list=No
             for m in meshList:
                 m['ver'] *=ratio
 
-            for s in skelList:
-                s *=ratio
+            if skelList is not None:
+                for s in skelList:
+                    s *=ratio
 
 
         else: