diff --git a/grpc_client/grpc_client.py b/grpc_client/grpc_client.py
index 74933cd..05a4dd7 100644
--- a/grpc_client/grpc_client.py
+++ b/grpc_client/grpc_client.py
@@ -252,24 +252,27 @@
             _ = __import__(modname)
 
     @inlineCallbacks
-    def invoke(self, stub, method_name, request, retry=1):
+    def invoke(self, stub, method_name, request, metadata, retry=1):
         """
         Invoke a gRPC call to the remote server and return the response.
         :param stub: Reference to the *_pb2 service stub
         :param method_name: The method name inside the service stub
         :param request: The request protobuf message
-        :return: The response protobuf message
+        :param metadata: [(str, str), (str, str), ...]
+        :return: The response protobuf message and returned trailing metadata
         """
 
         if not self.connected:
             raise ServiceUnavailable()
 
         try:
-            response = getattr(stub(self.channel), method_name)(request)
-            returnValue(response)
+            method = getattr(stub(self.channel), method_name)
+            response, rendezvous = method.with_call(request, metadata=metadata)
+            returnValue((response, rendezvous.trailing_metadata()))
 
         except grpc._channel._Rendezvous, e:
-            if e.code() == grpc.StatusCode.UNAVAILABLE:
+            code = e.code()
+            if code == grpc.StatusCode.UNAVAILABLE:
                 e = ServiceUnavailable()
 
                 if self.connected:
@@ -277,10 +280,17 @@
                     yield self.connect()
                     if retry > 0:
                         response = yield self.invoke(stub, method_name,
-                                                     request,
+                                                     request, metadata,
                                                      retry=retry - 1)
                         returnValue(response)
 
+            elif code in (
+                    grpc.StatusCode.NOT_FOUND,
+                    grpc.StatusCode.INVALID_ARGUMENT,
+                    grpc.StatusCode.ALREADY_EXISTS):
+
+                pass  # don't log error, these occur naturally
+
             else:
                 log.exception(e)
 
diff --git a/protoc_plugins/gw_gen.py b/protoc_plugins/gw_gen.py
index c5a8875..4400a1a 100755
--- a/protoc_plugins/gw_gen.py
+++ b/protoc_plugins/gw_gen.py
@@ -32,8 +32,7 @@
 
 from simplejson import dumps, load
 from structlog import get_logger
-from protobuf_to_dict import dict_to_protobuf
-from google.protobuf.json_format import MessageToDict
+from google.protobuf.json_format import MessageToDict, ParseDict
 from twisted.internet.defer import inlineCallbacks, returnValue
 
 {% set package = file_name.replace('.proto', '') %}
@@ -65,16 +64,16 @@
         {% elif method['body'] == '' %}
         data = kw
         {% else %}
-        riase NotImplementedError('cannot handle specific body field list')
+        raise NotImplementedError('cannot handle specific body field list')
         {% endif %}
         try:
-            req = dict_to_protobuf({{ type_map[method['input_type']] }}, data)
+            req = ParseDict(data, {{ type_map[method['input_type']] }}())
         except Exception, e:
             log.error('cannot-convert-to-protobuf', e=e, data=data)
             raise
-        res = yield grpc_client.invoke(
+        res, metadata = yield grpc_client.invoke(
             {{ type_map[method['service']] }}Stub,
-            '{{ method['method'] }}', req)
+            '{{ method['method'] }}', req, request.getAllHeaders().items())
         try:
             out_data = MessageToDict(res, True, True)
         except AttributeError, e:
@@ -83,6 +82,8 @@
                 f.write(res.SerializeToString())
             log.error('cannot-convert-from-protobuf', outdata_saved=filename)
             raise
+        for key, value in metadata:
+            request.setHeader(key, value)
         request.setHeader('Content-Type', 'application/json')
         log.debug('{{ method_name }}', **out_data)
         returnValue(dumps(out_data))
diff --git a/web_server/web_server.py b/web_server/web_server.py
index c96be0f..7e3d00d 100644
--- a/web_server/web_server.py
+++ b/web_server/web_server.py
@@ -17,6 +17,7 @@
 
 import os
 
+import grpc
 from klein import Klein
 from simplejson import dumps, load
 from structlog import get_logger
@@ -26,6 +27,8 @@
 from twisted.web.server import Site
 from twisted.web.static import File
 from werkzeug.exceptions import BadRequest
+from grpc import StatusCode
+
 
 log = get_logger()
 
@@ -97,3 +100,19 @@
             return File(os.path.join(self.work_dir, 'swagger.json'))
         except Exception, e:
             log.exception('file-not-found', request=request)
+
+    @app.handle_errors(grpc._channel._Rendezvous)
+    def grpc_exception(self, request, failure):
+        code = failure.value.code()
+        if code == StatusCode.NOT_FOUND:
+            request.setResponseCode(404)
+            return failure.value.details()
+        elif code == StatusCode.INVALID_ARGUMENT:
+            request.setResponseCode(400)
+            return failure.value.details()
+        elif code == StatusCode.ALREADY_EXISTS:
+            request.setResponseCode(409)
+            return failure.value.details()
+        else:
+            raise
+