diff --git a/spyne/model/_base.py b/spyne/model/_base.py
index 2a4db3687..4a7f73382 100644
--- a/spyne/model/_base.py
+++ b/spyne/model/_base.py
@@ -240,7 +240,8 @@ def set_method_config_do(self, what):
 
 class ModelBaseMeta(type(object)):
     def __getitem__(self, item):
-        return self.customize(**item)
+        if isinstance(item, dict):
+            return self.customize(**item)
 
     def customize(self, **kwargs):
         """Duplicates cls and overwrites the values in ``cls.Attributes`` with
diff --git a/spyne/protocol/soap/mime.py b/spyne/protocol/soap/mime.py
index d4aaa1de4..5223de454 100644
--- a/spyne/protocol/soap/mime.py
+++ b/spyne/protocol/soap/mime.py
@@ -72,7 +72,8 @@ def _join_attachment(ns_soap_env, href_id, envelope, payload, prefix=True):
     """
 
     # grab the XML element of the message in the SOAP body
-    soaptree = etree.fromstring(envelope)
+    xml_str_without_declaration = "\n".join(envelope.split("\n")[1:])
+    soaptree = etree.fromstring(xml_str_without_declaration)
     soapbody = soaptree.find("{%s}Body" % ns_soap_env)
 
     if soapbody is None:
@@ -215,9 +216,15 @@ def apply_mtom(headers, envelope, params, paramvals):
     """
 
     # grab the XML element of the message in the SOAP body
-    envelope = ''.join(envelope)
+    envelope = ''.join([b.decode("utf-8") for b in envelope])
+    xml_str_without_declaration = "\n".join(envelope.split("\n")[1:])
+
+    soaptree = etree.fromstring(xml_str_without_declaration)
+    for ns in soaptree.nsmap.items():
+        if 'soap' in ns[1]:
+            _ns_soap_env = ns[1]
+            break
 
-    soaptree = etree.fromstring(envelope)
     soapbody = soaptree.find("{%s}Body" % _ns_soap_env)
 
     message = None
@@ -266,7 +273,7 @@ def apply_mtom(headers, envelope, params, paramvals):
 
     # Extract attachments from SOAP envelope.
     for i in range(len(params)):
-        name, typ = params[i]
+        typ = params[i]
 
         if issubclass(typ, (ByteArray, File)):
             id = "SpyneAttachment_%s" % (len(mtompkg.get_payload()), )