diff --git a/oauth2/__init__.py b/oauth2/__init__.py
index a1776a75..77b4e5ee 100644
--- a/oauth2/__init__.py
+++ b/oauth2/__init__.py
@@ -372,7 +372,8 @@ def url(self, value):
                 raise ValueError("Unsupported URL %s (%s)." % (value, scheme))
 
             # Normalized URL excludes params, query, and fragment.
-            self.normalized_url = urlunsplit((scheme, netloc, path, None, None))
+            self.normalized_url = urlunsplit((scheme.lower(),
+                netloc.lower(), path, None, None))
         else:
             self.normalized_url = None
             self.__dict__['url'] = None
diff --git a/tests/test_oauth.py b/tests/test_oauth.py
index 58854564..f345c23c 100644
--- a/tests/test_oauth.py
+++ b/tests/test_oauth.py
@@ -364,6 +364,14 @@ def test_url(self):
         self.assertEqual(req.normalized_url, exp2)
         self.assertEqual(req.url, url2)
 
+    def test_url_lowercases_scheme_and_authority(self):
+        """Lowercase scheme and authority in URL normalization."""
+        # http://oauth.net/core/1.0a/#rfc.section.9.1.2
+        # https://github.com/joestump/python-oauth2/issues/29
+        url = 'HTTP://Example.com/resource'
+        req = oauth.Request("GET", url)
+        self.assertEquals(req.normalized_url, "http://example.com/resource")
+
     def test_bad_url(self):
         request = oauth.Request()
         try: