diff --git a/.gitignore b/.gitignore
index 7a958395..1c6eb47a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 .byebug_history
 .DS_Store
 .yardoc
+.ruby-version
 doc
 rdox
 coverage
diff --git a/lib/savon/builder.rb b/lib/savon/builder.rb
index 13a17ef6..69d6dcc1 100644
--- a/lib/savon/builder.rb
+++ b/lib/savon/builder.rb
@@ -38,18 +38,23 @@ def pretty
     end
 
     def build_document
-      xml_result = build_xml
+      # check if xml was already provided
+      if @locals.include? :xml
+        xml_result = @locals[:xml]
+      else
+        xml_result = build_xml
 
-      # if we have a signature sign the document
-      if @signature
-        @signature.document = xml_result
+        # if we have a signature sign the document
+        if @signature
+          @signature.document = xml_result
 
-        2.times do
-          @header = nil
-          @signature.document = build_xml
-        end
+          2.times do
+            @header             = nil
+            @signature.document = build_xml
+          end
 
-        xml_result = @signature.document
+          xml_result = @signature.document
+        end
       end
 
       # if there are attachments for the request, we should build a multipart message according to
@@ -70,7 +75,6 @@ def body_attributes
     end
 
     def to_s
-      return @locals[:xml] if @locals.include? :xml
       build_document
     end
 
@@ -254,15 +258,28 @@ def build_multipart_message(message_xml)
 
       # the mail.body.encoded algorithm reorders the parts, default order is [ "text/plain", "text/enriched", "text/html" ]
       # should redefine the sort order, because the soap request xml should be the first
-      multipart_message.body.set_sort_order [ "text/xml" ]
+      multipart_message.body.set_sort_order ['application/xop+xml', 'text/xml']
 
       multipart_message.body.encoded(multipart_message.content_transfer_encoding)
     end
 
     def init_multipart_message(message_xml)
       multipart_message = Mail.new
+
+      # MTOM differs from general SOAP attachments:
+      # 1. binary encoding
+      # 2. application/xop+xml mime type
+      if @locals[:mtom]
+        type = "application/xop+xml; charset=#{@globals[:encoding]}; type=\"text/xml\""
+
+        multipart_message.transport_encoding = 'binary'
+        message_xml.force_encoding('BINARY')
+      else
+        type = 'text/xml'
+      end
+
       xml_part = Mail::Part.new do
-        content_type 'text/xml'
+        content_type type
         body message_xml
         # in Content-Type the start parameter is recommended (RFC 2387)
         content_id '<soap-request-body@soap>'
diff --git a/lib/savon/operation.rb b/lib/savon/operation.rb
index 00e40d87..48872baa 100644
--- a/lib/savon/operation.rb
+++ b/lib/savon/operation.rb
@@ -101,9 +101,10 @@ def build_request(builder)
       request.body = builder.to_s
 
       if builder.multipart
-        request.gzip
+        type = @locals[:mtom] ? 'application/xop+xml"; start-info="text/xml' : SOAP_REQUEST_TYPE[@globals[:soap_version]]
+        request.gzip unless @locals[:mtom]
         request.headers["Content-Type"] = ["multipart/related",
-                                           "type=\"#{SOAP_REQUEST_TYPE[@globals[:soap_version]]}\"",
+                                           "type=\"#{type}\"",
                                            "start=\"#{builder.multipart[:start]}\"",
                                            "boundary=\"#{builder.multipart[:multipart_boundary]}\""].join("; ")
         request.headers["MIME-Version"] = "1.0"
diff --git a/lib/savon/options.rb b/lib/savon/options.rb
index 71d78666..0f472cb0 100644
--- a/lib/savon/options.rb
+++ b/lib/savon/options.rb
@@ -389,7 +389,8 @@ def initialize(options = {})
       defaults = {
         :advanced_typecasting => true,
         :response_parser      => :nokogiri,
-        :multipart            => false
+        :multipart            => false,
+        :mtom                 => false
       }
 
       super defaults.merge(options)
@@ -452,6 +453,11 @@ def attachments(attachments)
       @options[:attachments] = attachments
     end
 
+    # Instruct Savon to send attachments using MTOM https://www.w3.org/TR/soap12-mtom/
+    def mtom(mtom)
+      @options[:mtom] = mtom
+    end
+
     # Value of the SOAPAction HTTP header.
     def soap_action(soap_action)
       @options[:soap_action] = soap_action
@@ -477,6 +483,11 @@ def response_parser(parser)
       @options[:response_parser] = parser
     end
 
+    # Pass already configured Nori instance.
+    def nori(nori)
+      @options[:nori] = nori
+    end
+
     # Instruct Savon to create a multipart response if available.
     def multipart(multipart)
       @options[:multipart] = multipart
diff --git a/lib/savon/request_logger.rb b/lib/savon/request_logger.rb
index 079449ff..5404e82c 100644
--- a/lib/savon/request_logger.rb
+++ b/lib/savon/request_logger.rb
@@ -47,7 +47,7 @@ def headers_to_log(headers)
     end
 
     def body_to_log(body)
-      LogMessage.new(body, @globals[:filters], @globals[:pretty_print_xml]).to_s
+      LogMessage.new(body, @globals[:filters], @globals[:pretty_print_xml]).to_s.force_encoding(@globals[:encoding])
     end
 
   end
diff --git a/lib/savon/response.rb b/lib/savon/response.rb
index 9ca4a35b..e148182b 100644
--- a/lib/savon/response.rb
+++ b/lib/savon/response.rb
@@ -142,20 +142,16 @@ def xml_namespaces
     end
 
     def nori
-      return @nori if @nori
+      return @locals[:nori] if @locals[:nori]
 
-      nori_options = {
-        :delete_namespace_attributes => @globals[:delete_namespace_attributes],
-        :strip_namespaces            => @globals[:strip_namespaces],
-        :convert_tags_to             => @globals[:convert_response_tags_to],
-        :convert_attributes_to       => @globals[:convert_attributes_to],
-        :advanced_typecasting        => @locals[:advanced_typecasting],
-        :parser                      => @locals[:response_parser]
-      }
-
-      non_nil_nori_options = nori_options.reject { |_, value| value.nil? }
-      @nori = Nori.new(non_nil_nori_options)
+      @nori ||= Nori.new({
+                           :delete_namespace_attributes => @globals[:delete_namespace_attributes],
+                           :strip_namespaces            => @globals[:strip_namespaces],
+                           :convert_tags_to             => @globals[:convert_response_tags_to],
+                           :convert_attributes_to       => @globals[:convert_attributes_to],
+                           :advanced_typecasting        => @locals[:advanced_typecasting],
+                           :parser                      => @locals[:response_parser]
+                         }.reject { |_, value| value.nil? })
     end
-
   end
 end