diff --git a/lib/fog/aws/models/storage/file.rb b/lib/fog/aws/models/storage/file.rb
index 4dae684a9..6c5f9971b 100644
--- a/lib/fog/aws/models/storage/file.rb
+++ b/lib/fog/aws/models/storage/file.rb
@@ -27,7 +27,11 @@ module Fog
 
         # @note Chunk size to use for multipart uploads.
         #     Use small chunk sizes to minimize memory. E.g. 5242880 = 5mb
-        attr_accessor :multipart_chunk_size
+        attr_reader :multipart_chunk_size
+        def multipart_chunk_size=(mp_chunk_size)
+          raise ArgumentError.new("minimum multipart_chunk_size is 5242880") if mp_chunk_size < 5242880
+          @multipart_chunk_size = mp_chunk_size
+        end
 
         def acl
           requires :directory, :key
@@ -205,7 +209,10 @@ module Fog
           options['x-amz-storage-class'] = storage_class if storage_class
           options.merge!(encryption_headers)
 
-          if multipart_chunk_size && body.respond_to?(:read)
+          # With a single PUT operation you can upload objects up to 5 GB in size. Automatically set MP for larger objects.
+          multipart_chunk_size=5242880 if !multipart_chunk_size && Fog::Storage.get_body_size(body) > 5368709120
+
+          if multipart_chunk_size && Fog::Storage.get_body_size(body) >= multipart_chunk_size && body.respond_to?(:read)
             data = multipart_save(options)
             merge_attributes(data.body)
           else