diff --git a/requests/models.py b/requests/models.py
index e2055fe2..ac99822f 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -328,8 +328,9 @@ class PreparedRequest(RequestEncodingMixin, RequestHooksMixin):
     def prepare_method(self, method):
         """Prepares the given HTTP method."""
         self.method = method
-        if self.method is not None:
-            self.method = self.method.upper()
+        if self.method is None:
+            raise ValueError('Request method cannot be "None"')
+        self.method = to_native_string(self.method).upper()
 
     def prepare_url(self, url, params):
         """Prepares the given HTTP URL."""
diff --git a/requests/sessions.py b/requests/sessions.py
index 820919ee..4c744eea 100644
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -432,9 +432,6 @@ class Session(SessionRedirectMixin):
         :param cert: (optional) if String, path to ssl client cert file (.pem).
             If Tuple, ('cert', 'key') pair.
         """
-
-        method = to_native_string(method)
-
         # Create the Request.
         req = Request(
             method = method.upper(),
diff --git a/test_requests.py b/test_requests.py
index cad8c055..1053666e 100755
--- a/test_requests.py
+++ b/test_requests.py
@@ -89,7 +89,7 @@ class RequestsTestCase(unittest.TestCase):
             requests.get('http://')
 
     def test_basic_building(self):
-        req = requests.Request()
+        req = requests.Request(method='GET')
         req.url = 'http://kennethreitz.org/'
         req.data = {'life': '42'}
 
@@ -813,7 +813,7 @@ class RequestsTestCase(unittest.TestCase):
         assert ('user', 'pass#pass') == requests.utils.get_auth_from_url(url)
 
     def test_cannot_send_unprepared_requests(self):
-        r = requests.Request(url=HTTPBIN)
+        r = requests.Request(method='GET', url=HTTPBIN)
         with pytest.raises(ValueError):
             requests.Session().send(r)
 
@@ -1617,6 +1617,16 @@ def test_prepare_unicode_url():
     assert_copy(p, p.copy())
 
 
+def test_prepare_requires_a_request_method():
+    req = requests.Request()
+    with pytest.raises(ValueError):
+        req.prepare()
+
+    prepped = PreparedRequest()
+    with pytest.raises(ValueError):
+        prepped.prepare()
+
+
 def test_urllib3_retries():
     from requests.packages.urllib3.util import Retry
     s = requests.Session()