diff --git a/moto/moto_proxy/utils.py b/moto/moto_proxy/utils.py
index 1667a919e..6f7ef2d41 100644
--- a/moto/moto_proxy/utils.py
+++ b/moto/moto_proxy/utils.py
@@ -88,7 +88,7 @@ def get_body_from_form_data(
     headers: Dict[str, str] = {}
 
     for part in parts:
-        if data is not None:
+        if data is None:
             for header in part.headers:
                 if b'name="upload_file"' in header.value:
                     headers["key"] = "upload_file"