diff --git a/lib/s3/right_s3.rb b/lib/s3/right_s3.rb
index f6d275a..79502a5 100644
--- a/lib/s3/right_s3.rb
+++ b/lib/s3/right_s3.rb
@@ -541,11 +541,11 @@ def put(data=nil, perms=nil, headers={}, &blck)
         #  key.data = upload_data
         #  key.put_multipart(:part_size => 5*1024*1024)             #=> true
         #
-      def put_multipart(data=nil, perms=nil, headers={}, part_size=nil)
+      def put_multipart(data=nil, perms=nil, headers={}, part_size=nil, &block)
         headers['x-amz-acl'] = perms if perms
         @data = data || @data
         meta  = self.class.add_meta_prefix(@meta_headers)
-        @bucket.s3.interface.store_object_multipart({:bucket => @bucket.name, :key => @name, :data => @data, :headers => meta.merge(headers), :part_size => part_size})
+        @bucket.s3.interface.store_object_multipart({:bucket => @bucket.name, :key => @name, :data => @data, :headers => meta.merge(headers), :part_size => part_size}, &block)
       end
       
         # Rename an object. Returns new object name.
diff --git a/lib/s3/right_s3_interface.rb b/lib/s3/right_s3_interface.rb
index 4f21511..3d2471d 100644
--- a/lib/s3/right_s3_interface.rb
+++ b/lib/s3/right_s3_interface.rb
@@ -600,6 +600,7 @@ def store_object_multipart(params)
               send_part_hash = generate_rest_request('PUT', params[:headers].merge({ :url=>"#{params[:bucket]}/#{CGI::escape params[:key]}?partNumber=#{index}&uploadId=#{upload_id}", :data=>part_data } ))
               send_part_resp = request_info(send_part_hash, S3HttpResponseHeadParser.new)
               part_etags << {:part_num => index, :etag => send_part_resp['etag']}
+              yield(part_data) if block_given?
               index += 1
               break # successful, can move to next part
             rescue AwsError => e