diff --git a/sanic/exceptions.py b/sanic/exceptions.py
index 8998aab8..21ab2a94 100644
--- a/sanic/exceptions.py
+++ b/sanic/exceptions.py
@@ -209,25 +209,43 @@ class Unauthorized(SanicException):
     Unauthorized exception (401 HTTP status code).
 
     :param scheme: Name of the authentication scheme to be used.
-    :param realm: Description of the protected area. (optional)
     :param challenge: A dict containing values to add to the WWW-Authenticate
-                      header that is generated. This is especially useful when
-                      dealing with the Digest scheme. (optional)
+        header that is generated. This is especially useful when dealing with
+        the Digest scheme. (optional)
+
+    Examples::
+
+        # With a Basic auth-scheme, realm MUST be present:
+        challenge = {"realm": "Restricted Area"}
+        raise Unauthorized("Auth required.", "Basic", challenge)
+
+        # With a Digest auth-scheme, things are a bit more complicated:
+        challenge = {
+            "realm": "Restricted Area",
+            "qop": "auth, auth-int",
+            "algorithm": "MD5",
+            "nonce": "abcdef",
+            "opaque": "zyxwvu"
+        }
+        raise Unauthorized("Auth required.", "Digest", challenge)
+
+        # With a Bearer auth-scheme, realm is optional:
+        challenge = {"realm": "Restricted Area"}
+        raise Unauthorized("Auth required.", "Bearer", challenge)
     """
     pass
 
-    def __init__(self, message, scheme, realm="", challenge=None):
+    def __init__(self, message, scheme, challenge=None):
         super().__init__(message)
 
-        adds = ""
+        chal = ""
 
         if challenge is not None:
             values = ["{!s}={!r}".format(k, v) for k, v in challenge.items()]
-            adds = ', '.join(values)
-            adds = ', {}'.format(adds)
+            chal = ', '.join(values)
 
         self.headers = {
-            "WWW-Authenticate": "{} realm='{}'{}".format(scheme, realm, adds)
+            "WWW-Authenticate": "{} {}".format(scheme, chal).rstrip()
         }
 
 
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 45bdab88..620e7891 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -33,17 +33,22 @@ def exception_app():
 
     @app.route('/401/basic')
     def handler_401_basic(request):
-        raise Unauthorized("Unauthorized", "Basic", "Sanic")
+        raise Unauthorized("Unauthorized", "Basic", {"realm": "Sanic"})
 
     @app.route('/401/digest')
     def handler_401_digest(request):
         challenge = {
+            "realm": "Sanic",
             "qop": "auth, auth-int",
             "algorithm": "MD5",
             "nonce": "abcdef",
             "opaque": "zyxwvu",
         }
-        raise Unauthorized("Unauthorized", "Digest", "Sanic", challenge)
+        raise Unauthorized("Unauthorized", "Digest", challenge)
+
+    @app.route('/401/bearer')
+    def handler_401_bearer(request):
+        raise Unauthorized("Unauthorized", "Bearer")
 
     @app.route('/invalid')
     def handler_invalid(request):
@@ -136,6 +141,10 @@ def test_unauthorized_exception(exception_app):
     assert "nonce='abcdef'" in auth_header
     assert "opaque='zyxwvu'" in auth_header
 
+    request, response = exception_app.test_client.get('/401/bearer')
+    assert response.status == 401
+    assert response.headers.get('WWW-Authenticate') == "Bearer"
+
 
 def test_handled_unhandled_exception(exception_app):
     """Test that an exception not built into sanic is handled"""