diff --git a/apiclient/http.py b/apiclient/http.py
index d590d1b..cd279b1 100644
--- a/apiclient/http.py
+++ b/apiclient/http.py
@@ -671,9 +671,8 @@
         self.body = parsed.query
         self.headers['content-length'] = str(len(self.body))
 
-      resp, content = http.request(self.uri, method=self.method,
-                                   body=self.body,
-                                   headers=self.headers)
+      resp, content = http.request(str(self.uri), method=str(self.method),
+                                   body=self.body, headers=self.headers)
       if resp.status >= 300:
         raise HttpError(resp, content, uri=self.uri)
     return self.postproc(resp, content)
@@ -1353,7 +1352,7 @@
 class HttpMock(object):
   """Mock of httplib2.Http"""
 
-  def __init__(self, filename, headers=None):
+  def __init__(self, filename=None, headers=None):
     """
     Args:
       filename: string, absolute filename to read response from
@@ -1361,10 +1360,19 @@
     """
     if headers is None:
       headers = {'status': '200 OK'}
-    f = file(filename, 'r')
-    self.data = f.read()
-    f.close()
-    self.headers = headers
+    if filename:
+      f = file(filename, 'r')
+      self.data = f.read()
+      f.close()
+    else:
+      self.data = None
+    self.response_headers = headers
+    self.headers = None
+    self.uri = None
+    self.method = None
+    self.body = None
+    self.headers = None
+
 
   def request(self, uri,
               method='GET',
@@ -1372,7 +1380,11 @@
               headers=None,
               redirections=1,
               connection_type=None):
-    return httplib2.Response(self.headers), self.data
+    self.uri = uri
+    self.method = method
+    self.body = body
+    self.headers = headers
+    return httplib2.Response(self.response_headers), self.data
 
 
 class HttpMockSequence(object):
diff --git a/oauth2client/client.py b/oauth2client/client.py
index cce4ae6..1b0f828 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -89,6 +89,11 @@
   pass
 
 
+class NonAsciiHeaderError(Error):
+  """Header names and values must be ASCII strings."""
+  pass
+
+
 def _abstract():
   raise NotImplementedError('You need to override this function')
 
@@ -319,6 +324,28 @@
       self.release_lock()
 
 
+def clean_headers(headers):
+  """Forces header keys and values to be strings, i.e not unicode.
+
+  The httplib module just concats the header keys and values in a way that may
+  make the message header a unicode string, which, if it then tries to
+  contatenate to a binary request body may result in a unicode decode error.
+
+  Args:
+    headers: dict, A dictionary of headers.
+
+  Returns:
+    The same dictionary but with all the keys converted to strings.
+  """
+  clean = {}
+  try:
+    for k, v in headers.iteritems():
+      clean[str(k)] = str(v)
+  except UnicodeEncodeError:
+    raise NonAsciiHeaderError(k + ': ' + v)
+  return clean
+
+
 class OAuth2Credentials(Credentials):
   """Credentials object for OAuth 2.0.
 
@@ -416,7 +443,7 @@
         else:
           headers['user-agent'] = self.user_agent
 
-      resp, content = request_orig(uri, method, body, headers,
+      resp, content = request_orig(uri, method, body, clean_headers(headers),
                                    redirections, connection_type)
 
       # Older API (GData) respond with 403
@@ -424,7 +451,7 @@
         logger.info('Refreshing due to a %s' % str(resp.status))
         self._refresh(request_orig)
         self.apply(headers)
-        return request_orig(uri, method, body, headers,
+        return request_orig(uri, method, body, clean_headers(headers),
                             redirections, connection_type)
       else:
         return (resp, content)
diff --git a/tests/test_http.py b/tests/test_http.py
index 3609f40..81248eb 100644
--- a/tests/test_http.py
+++ b/tests/test_http.py
@@ -483,6 +483,26 @@
     self.exceptions[request_id] = exception
 
 
+class TestHttpRequest(unittest.TestCase):
+  def test_unicode(self):
+    http = HttpMock(datafile('zoo.json'), headers={'status': '200'})
+    model = JsonModel()
+    uri = u'https://www.googleapis.com/someapi/v1/collection/?foo=bar'
+    method = u'POST'
+    request = HttpRequest(
+        http,
+        model.response,
+        uri,
+        method=method,
+        body=u'{}',
+        headers={'content-type': 'application/json'})
+    request.execute()
+    self.assertEqual(uri, http.uri)
+    self.assertEqual(str, type(http.uri))
+    self.assertEqual(method, http.method)
+    self.assertEqual(str, type(http.method))
+
+
 class TestBatch(unittest.TestCase):
 
   def setUp(self):
diff --git a/tests/test_oauth2client.py b/tests/test_oauth2client.py
index 8f855d4..2de87a1 100644
--- a/tests/test_oauth2client.py
+++ b/tests/test_oauth2client.py
@@ -34,6 +34,7 @@
 except ImportError:
     from cgi import parse_qs
 
+from apiclient.http import HttpMock
 from apiclient.http import HttpMockSequence
 from oauth2client.anyjson import simplejson
 from oauth2client.clientsecrets import _loadfile
@@ -44,13 +45,14 @@
 from oauth2client.client import Credentials
 from oauth2client.client import FlowExchangeError
 from oauth2client.client import MemoryCache
+from oauth2client.client import NonAsciiHeaderError
 from oauth2client.client import OAuth2Credentials
 from oauth2client.client import OAuth2WebServerFlow
 from oauth2client.client import OOB_CALLBACK_URN
 from oauth2client.client import VerifyJwtTokenError
 from oauth2client.client import _extract_id_token
-from oauth2client.client import credentials_from_code
 from oauth2client.client import credentials_from_clientsecrets_and_code
+from oauth2client.client import credentials_from_code
 from oauth2client.client import flow_from_clientsecrets
 
 DATA_DIR = os.path.join(os.path.dirname(__file__), 'data')
@@ -86,7 +88,7 @@
     restored = Credentials.new_from_json(json)
 
 
-class OAuth2CredentialsTests(unittest.TestCase):
+class BasicCredentialsTests(unittest.TestCase):
 
   def setUp(self):
     access_token = "foo"
@@ -146,6 +148,35 @@
 
     self.assertEqual(instance.__dict__, self.credentials.__dict__)
 
+  def test_no_unicode_in_request_params(self):
+    access_token = u'foo'
+    client_id = u'some_client_id'
+    client_secret = u'cOuDdkfjxxnv+'
+    refresh_token = u'1/0/a.df219fjls0'
+    token_expiry = unicode(datetime.datetime.utcnow())
+    token_uri = u'https://www.google.com/accounts/o8/oauth2/token'
+    user_agent = u'refresh_checker/1.0'
+    credentials = OAuth2Credentials(access_token, client_id, client_secret,
+                                    refresh_token, token_expiry, token_uri,
+                                    user_agent)
+
+    http = HttpMock(headers={'status': '200'})
+    http = credentials.authorize(http)
+    http.request(u'http://example.com', method=u'GET', headers={
+        u'foo': u'bar'
+        })
+    for k, v in http.headers.iteritems():
+      self.assertEqual(str, type(k))
+      self.assertEqual(str, type(v))
+
+    # Test again with unicode strings that can't simple be converted to ASCII.
+    try:
+      http.request(
+          u'http://example.com', method=u'GET', headers={u'foo': u'\N{COMET}'})
+      self.fail('Expected exception to be raised.')
+    except NonAsciiHeaderError:
+      pass
+
 
 class AccessTokenCredentialsTests(unittest.TestCase):