diff --git a/wsme/rest/args.py b/wsme/rest/args.py
index 55fb4eb..5268e86 100644
--- a/wsme/rest/args.py
+++ b/wsme/rest/args.py
@@ -233,7 +233,8 @@ def args_from_body(funcdef, body, mimetype):
     elif mimetype in restxml.accept_content_types:
         dataformat = restxml
     else:
-        raise ValueError("Unknown mimetype: %s" % mimetype)
+        raise ClientSideError("Unknown mimetype: %s" % mimetype,
+                              status_code=415)
 
     try:
         kw = dataformat.parse(
diff --git a/wsme/root.py b/wsme/root.py
index 1ccfbdf..c31ad96 100644
--- a/wsme/root.py
+++ b/wsme/root.py
@@ -203,6 +203,7 @@ class WSRoot(object):
             infos = wsme.api.format_exception(sys.exc_info(), self._debug)
             if isinstance(e, ClientSideError):
                 request.client_errorcount += 1
+                request.client_last_status_code = e.code
             else:
                 request.server_errorcount += 1
             return protocol.encode_error(context, infos)
@@ -266,6 +267,7 @@ class WSRoot(object):
 
         request.calls = []
         request.client_errorcount = 0
+        request.client_last_status_code = None
         request.server_errorcount = 0
 
         try:
@@ -290,7 +292,9 @@ class WSRoot(object):
                 if hasattr(protocol, 'get_response_status'):
                     res.status = protocol.get_response_status(request)
                 else:
-                    if request.client_errorcount:
+                    if request.client_errorcount == 1:
+                        res.status = request.client_last_status_code
+                    elif request.client_errorcount:
                         res.status = 400
                     elif request.server_errorcount:
                         res.status = 500
diff --git a/wsme/tests/test_restjson.py b/wsme/tests/test_restjson.py
index 8099ff1..b1a91d9 100644
--- a/wsme/tests/test_restjson.py
+++ b/wsme/tests/test_restjson.py
@@ -250,6 +250,15 @@ class TestRestJson(wsme.tests.protocol.RestOnlyProtocolTestCase):
         print(r)
         assert json.loads(r.text) == 2
 
+    def test_invalid_content_type_body(self):
+        r = self.app.post('/argtypes/setint.json', '{"value": 2}',
+                          headers={"Content-Type": "application/invalid"},
+                          expect_errors=True)
+        print(r)
+        assert r.status_int == 415
+        assert json.loads(r.text)['faultstring'] == \
+            "Unknown mimetype: application/invalid"
+
     def test_invalid_json_body(self):
         r = self.app.post('/argtypes/setint.json', '{"value": 2',
                           headers={"Content-Type": "application/json"},