diff --git a/pyVmomi/SoapAdapter.py b/pyVmomi/SoapAdapter.py
index f2380acd7..0bec26e7d 100644
--- a/pyVmomi/SoapAdapter.py
+++ b/pyVmomi/SoapAdapter.py
@@ -99,6 +99,11 @@
 ## Localized MethodFault type
 LocalizedMethodFault = GetVmodlType("vmodl.LocalizedMethodFault")
 
+def encode(string, encoding):
+    if PY2:
+        return string.encode(encoding)
+    return u(string)
+
 ## Escape <, >, &
 def XmlEscape(xmlStr):
     escaped = xmlStr.replace("&", "&amp;").replace(">", "&gt;").replace("<", "&lt;")
@@ -316,7 +321,7 @@ def _Serialize(self, val, info, defNS):
          ns, name = GetQualifiedWsdlName(Type(val))
          attr += ' type="{0}"'.format(name)
          self.writer.write('<{0}{1}>{2}</{3}>'.format(info.name, attr,
-                                              val._moId.encode(self.encoding),
+                                              encode(val._moId, self.encoding),
                                               info.name))
       elif isinstance(val, list):
          if info.type is object:
@@ -399,7 +404,8 @@ def _Serialize(self, val, info, defNS):
                val = val.decode('UTF-8')
          result = XmlEscape(val)
          self.writer.write('<{0}{1}>{2}</{0}>'.format(info.name, attr,
-                                                      result.encode(self.encoding)))
+                                                      encode(result,
+                                                             self.encoding)))
 
    ## Serialize a a data object (internal)
    #
@@ -576,7 +582,11 @@ def StartElementHandler(self, tag, attr):
       if not self.stack:
          if self.isFault:
             ns, name = self.SplitTag(tag)
-            objType = self.LookupWsdlType(ns, name[:-5])
+            try:
+               objType = self.LookupWsdlType(ns, name[:-5])
+            except KeyError:
+               message = "{0} was not found in the WSDL".format(name[:-5])
+               raise VmomiMessageFault(message)
             # Only top level soap fault should be deserialized as method fault
             deserializeAsLocalizedMethodFault = False
          else:
diff --git a/tests/fixtures/test_simple_request_serializer.yaml b/tests/fixtures/test_simple_request_serializer.yaml
new file mode 100644
index 000000000..23df89432
--- /dev/null
+++ b/tests/fixtures/test_simple_request_serializer.yaml
@@ -0,0 +1,44 @@
+interactions:
+- request:
+    body: '<?xml version="1.0" encoding="UTF-8"?>
+
+      <soapenv:Envelope xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
+      xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+
+      <soapenv:Body><RetrieveServiceContent xmlns="urn:vim25"><_this type="ServiceInstance">ServiceInstance</_this></RetrieveServiceContent></soapenv:Body>
+
+      </soapenv:Envelope>'
+    headers:
+      Accept-Encoding: ['gzip, deflate']
+      Content-Type: [text/xml; charset=UTF-8]
+      Cookie: ['']
+      SOAPAction: ['"urn:vim2/2.0"']
+    method: POST
+    uri: https://vcsa:443/sdk
+  response:
+    body: {string: "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<soapenv:Envelope
+        xmlns:soapenc=\"http://schemas.xmlsoap.org/soap/encoding/\"\n xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\"\n
+        xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"\n xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">\n<soapenv:Body>\n<RetrieveServiceContentResponse
+        xmlns=\"urn:vim2\"><returnval><rootFolder type=\"Folder\">group-d1</rootFolder><propertyCollector
+        type=\"PropertyCollector\">propertyCollector</propertyCollector><about><name>VMware
+        vCenter Server</name><fullName>VMware vCenter Server 5.5.0 build-1750787 (Sim)</fullName><vendor>VMware,
+        Inc.</vendor><version>5.5.0</version><build>1750787 (Sim)</build><localeVersion>INTL</localeVersion><localeBuild>000</localeBuild><osType>linux-x64</osType><productLineId>vpx</productLineId><apiType>VirtualCenter</apiType><apiVersion>5.5</apiVersion></about><setting
+        type=\"OptionManager\">VpxSettings</setting><userDirectory type=\"UserDirectory\">UserDirectory</userDirectory><sessionManager
+        type=\"SessionManager\">SessionManager</sessionManager><authorizationManager
+        type=\"AuthorizationManager\">AuthorizationManager</authorizationManager><perfManager
+        type=\"PerformanceManager\">PerfMgr</perfManager><scheduledTaskManager type=\"ScheduledTaskManager\">ScheduledTaskManager</scheduledTaskManager><alarmManager
+        type=\"AlarmManager\">AlarmManager</alarmManager><eventManager type=\"EventManager\">EventManager</eventManager><taskManager
+        type=\"TaskManager\">TaskManager</taskManager><customizationSpecManager type=\"CustomizationSpecManager\">CustomizationSpecManager</customizationSpecManager><customFieldsManager
+        type=\"CustomFieldsManager\">CustomFieldsManager</customFieldsManager><diagnosticManager
+        type=\"DiagnosticManager\">DiagMgr</diagnosticManager><licenseManager type=\"LicenseManager\">LicenseManager</licenseManager><searchIndex
+        type=\"SearchIndex\">SearchIndex</searchIndex></returnval></RetrieveServiceContentResponse>\n</soapenv:Body>\n</soapenv:Envelope>"}
+    headers:
+      Cache-Control: [no-cache]
+      Connection: [Keep-Alive]
+      Content-Length: ['1948']
+      Content-Type: [text/xml; charset=utf-8]
+      Date: ['Mon, 28 Jul 2014 22:02:17 GMT']
+      Set-Cookie: ['vmware_soap_session="52d2bdd9-aec7-5f5c-652e-09737979ce13"; Path=/;
+          HttpOnly; Secure; ']
+    status: {code: 200, message: OK}
+version: 1
diff --git a/tests/test_serializer.py b/tests/test_serializer.py
new file mode 100644
index 000000000..c7c1bf4af
--- /dev/null
+++ b/tests/test_serializer.py
@@ -0,0 +1,54 @@
+# VMware vSphere Python SDK
+# Copyright (c) 2008-2014 VMware, Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from tests import fixtures_path
+import unittest
+import vcr
+
+
+from pyVmomi import SoapStubAdapter
+from pyVmomi import vim
+
+class SerializerTests(unittest.TestCase):
+
+    def test_simple_request_serializer(self):
+        def request_matcher(r1, r2):
+            soap_msg = ('<soapenv:Body>'
+                        '<RetrieveServiceContent xmlns="urn:vim25">'
+                        '<_this type="ServiceInstance">'
+                        'ServiceInstance'
+                        '</_this>'
+                        '</RetrieveServiceContent>'
+                        '</soapenv:Body>')
+            if soap_msg in r1.body:
+                return True
+            raise SystemError('serialization error occurred')
+
+        my_vcr = vcr.VCR()
+        my_vcr.register_matcher('request_matcher', request_matcher)
+
+        with my_vcr.use_cassette(
+                'test_simple_request_serializer.yaml',
+                cassette_library_dir=fixtures_path,
+                record_mode='none',
+                match_on=['request_matcher']) as cass:
+            host = 'vcsa'
+            port = 443
+            stub = SoapStubAdapter(host, port)
+            si = vim.ServiceInstance("ServiceInstance", stub)
+            content = si.RetrieveContent()
+            self.assertTrue(content is not None)
+            self.assertTrue(
+                '<_this type="ServiceInstance">ServiceInstance</_this>'
+                in cass.requests[0].body)
\ No newline at end of file