diff --git a/moto/s3/models.py b/moto/s3/models.py
index a97e28627..9ab0a5b8b 100644
--- a/moto/s3/models.py
+++ b/moto/s3/models.py
@@ -60,16 +60,15 @@ class FakeMultipart(object):
         self.parts = {}
         self.id = base64.b64encode(os.urandom(43)).replace('=', '').replace('+', '')
 
-
     def complete(self):
         total = bytearray()
+        last_part_name = len(self.list_parts())
 
         for part in self.list_parts():
+            if part.name != last_part_name and len(part.value) < 5242880:
+                return
             total.extend(part.value)
 
-        if len(total) < 5242880:
-            return
-
         return total
 
     def set_part(self, part_id, value):