diff --git a/unittests/test_server_side_scripting.py b/unittests/test_server_side_scripting.py
index 1fb24d7e40bb843391a971c5f69680b541e1de0e..b699c4482d02972282167eb9683a956097ebc5e9 100644
--- a/unittests/test_server_side_scripting.py
+++ b/unittests/test_server_side_scripting.py
@@ -46,7 +46,7 @@ def setup_module():
         content_type = kwargs["headers"]["Content-Type"]
 
         if content_type.startswith("multipart/form-data; boundary"):
-            parts = kwargs["body"]
+            parts = kwargs["body"].multipart_yielder
             stdout = []
             for part in parts:
                 if hasattr(part, "decode"):