diff --git a/wsme/controller.py b/wsme/controller.py
index d3707e4..303dd6e 100644
--- a/wsme/controller.py
+++ b/wsme/controller.py
@@ -81,6 +81,7 @@ class FunctionDefinition(object):
                 return arg
         return None
 
+
 def register_protocol(protocol):
     global registered_protocols
     registered_protocols[protocol.name] = protocol
@@ -155,7 +156,9 @@ class WSRoot(object):
     def _select_protocol(self, request):
         log.debug("Selecting a protocol for the following request :\n"
                   "headers: %s\nbody: %s", request.headers,
-                  len(request.body) > 512 and request.body[:512] or request.body)
+                  len(request.body) > 512
+                  and request.body[:512]
+                  or request.body)
         protocol = None
         if 'wsmeproto' in request.params:
             protocol = self.protocols[request.params['wsmeproto']]
@@ -176,7 +179,8 @@ class WSRoot(object):
                 msg = ("None of the following protocols can handle this "
                        "request : %s" % ','.join(self.protocols.keys()))
                 res.status = 500
-                res.text = msg
+                res.content_type = 'text/plain'
+                res.body = msg
                 log.error(msg)
                 return res
             path = protocol.extract_path(request)
diff --git a/wsme/tests/protocol.py b/wsme/tests/protocol.py
index db76eb9..8a59185 100644
--- a/wsme/tests/protocol.py
+++ b/wsme/tests/protocol.py
@@ -229,7 +229,8 @@ class ProtocolTestCase(unittest.TestCase):
             assert "No error raised"
         except CallException, e:
             assert e.faultcode == 'Client'
-            assert e.faultstring.lower() == u'unknown function name: invalid_function'
+            assert e.faultstring.lower() == \
+                    u'unknown function name: invalid_function'
 
     def test_serverside_error(self):
         try:
@@ -242,7 +243,7 @@ class ProtocolTestCase(unittest.TestCase):
 
     def test_touch(self):
         r = self.call('touch')
-        assert r is None, r 
+        assert r is None, r
 
     def test_return_str(self):
         r = self.call('returntypes/getstr')
@@ -369,3 +370,17 @@ class ProtocolTestCase(unittest.TestCase):
                          value=(value, [NestedOuter]),
                          _rt=[NestedOuter])
         assert r == value
+
+    def test_missing_argument(self):
+        try:
+            r = self.call('argtypes/setdatetime')
+            assert "No error raised"
+        except CallException, e:
+            print e
+            assert e.faultcode == 'Client'
+            assert e.faultstring == u'Missing argument: "value"'
+
+    def test_html_format(self):
+        res = self.call('argtypes/setdatetime', _accept="text/html",
+            _no_result_decode=True)
+        assert res.content_type == 'text/html', res.content_type
diff --git a/wsme/tests/test_controller.py b/wsme/tests/test_controller.py
index 8e01bcb..1a42eac 100644
--- a/wsme/tests/test_controller.py
+++ b/wsme/tests/test_controller.py
@@ -73,7 +73,7 @@ class TestController(unittest.TestCase):
 
         r = WSRoot()
         assert len(r.protocols) == 0
-        
+
         r.addprotocol('dummy')
         assert r.protocols['dummy']
 
@@ -134,3 +134,32 @@ class TestController(unittest.TestCase):
 
         assert p.lastreq.path == '/touch'
         assert p.hits == 2
+
+    def test_no_available_protocol(self):
+        r = WSRoot()
+
+        app = webtest.TestApp(r)
+
+        res = app.get('/', expect_errors=True)
+        assert res.status_int == 500
+        print res.body
+        assert res.body.find(
+            "None of the following protocols can handle this request") != -1
+
+    def test_return_content_type_guess(self):
+        class DummierProto(DummyProtocol):
+            content_types = ['text/xml', 'text/plain']
+
+        r = WSRoot([DummierProto()])
+
+        app = webtest.TestApp(r)
+
+        res = app.get('/', expect_errors=True, headers={
+            'Accept': 'text/xml,q=0.8'})
+        assert res.status_int == 400
+        assert res.content_type == 'text/xml', res.content_type
+
+        res = app.get('/', expect_errors=True, headers={
+            'Accept': 'text/plain'})
+        assert res.status_int == 400
+        assert res.content_type == 'text/plain', res.content_type
diff --git a/wsme/tests/test_restjson.py b/wsme/tests/test_restjson.py
index 3aa59d5..20b7fec 100644
--- a/wsme/tests/test_restjson.py
+++ b/wsme/tests/test_restjson.py
@@ -49,7 +49,8 @@ def prepare_result(value, datatype):
 class TestRestJson(wsme.tests.protocol.ProtocolTestCase):
     protocol = 'REST+Json'
 
-    def call(self, fpath, _rt=None, **kw):
+    def call(self, fpath, _rt=None, _accept=None,
+                _no_result_decode=False, **kw):
         for key in kw:
             if isinstance(kw[key], tuple):
                 value, datatype = kw[key]
@@ -58,14 +59,21 @@ class TestRestJson(wsme.tests.protocol.ProtocolTestCase):
                 datatype = type(value)
             kw[key] = prepare_value(value, datatype)
         content = json.dumps(kw)
+        headers = {
+            'Content-Type': 'application/json',
+        }
+        if _accept is not None:
+            headers["Accept"] = _accept
         res = self.app.post(
             '/' + fpath,
             content,
-            headers={
-                'Content-Type': 'application/json',
-            },
+            headers=headers,
             expect_errors=True)
         print "Received:", res.body
+
+        if _no_result_decode:
+            return res
+
         r = json.loads(res.body)
         if 'result' in r:
             r = r['result']
diff --git a/wsme/tests/test_restxml.py b/wsme/tests/test_restxml.py
index 0b974c9..67b91af 100644
--- a/wsme/tests/test_restxml.py
+++ b/wsme/tests/test_restxml.py
@@ -72,17 +72,25 @@ def loadxml(el, datatype):
 class TestRestXML(wsme.tests.protocol.ProtocolTestCase):
     protocol = 'REST+XML'
 
-    def call(self, fpath, _rt=None, **kw):
+    def call(self, fpath, _rt=None, _accept=None,
+                _no_result_decode=False, **kw):
         el = dumpxml('parameters', kw)
         content = et.tostring(el)
+        headers = {
+            'Content-Type': 'text/xml',
+        }
+        if _accept is not None:
+            headers['Accept'] = _accept
         res = self.app.post(
             '/' + fpath,
             content,
-            headers={
-                'Content-Type': 'text/xml',
-            },
+            headers=headers,
             expect_errors=True)
         print "Received:", res.body
+
+        if _no_result_decode:
+            return res
+
         el = et.fromstring(res.body)
         if el.tag == 'error':
             raise wsme.tests.protocol.CallException(
diff --git a/wsme/tests/test_soap.py b/wsme/tests/test_soap.py
index b8bffa5..8d86c57 100644
--- a/wsme/tests/test_soap.py
+++ b/wsme/tests/test_soap.py
@@ -145,7 +145,8 @@ class TestSOAP(wsme.tests.protocol.ProtocolTestCase):
         print res.body
         assert res.status.startswith('200')
 
-    def call(self, fpath, _rt=None, **kw):
+    def call(self, fpath, _rt=None, _accept=None,
+                _no_result_decode=False, **kw):
         path = fpath.strip('/').split('/')
         # get the actual definition so we can build the adequate request
         if kw:
@@ -159,11 +160,17 @@ class TestSOAP(wsme.tests.protocol.ProtocolTestCase):
         methodname = ''.join((i.capitalize() for i in path))
         message = build_soap_message(methodname, params)
         print message
+        headers = {"Content-Type": "application/soap+xml; charset=utf-8"}
+        if _accept is not None:
+            headers['Accept'] = _accept
         res = self.app.post('/', message,
-            headers={"Content-Type": "application/soap+xml; charset=utf-8"},
+            headers=headers,
             expect_errors=True)
         print "Status: ", res.status, "Received:", res.body
 
+        if _no_result_decode:
+            return res
+
         el = et.fromstring(res.body)
         body = el.find(body_qn)
         print body