diff --git a/msal/authority.py b/msal/authority.py
index 689ea8cb..51289d2c 100644
--- a/msal/authority.py
+++ b/msal/authority.py
@@ -1,10 +1,12 @@
 import re
+import logging
 
 import requests
 
 from .exceptions import MsalServiceError
 
 
+logger = logging.getLogger(__name__)
 WORLD_WIDE = 'login.microsoftonline.com'  # There was an alias login.windows.net
 WELL_KNOWN_AUTHORITY_HOSTS = set([
     WORLD_WIDE,
@@ -38,7 +40,7 @@ def __init__(self, authority_url, validate_authority=True,
         canonicalized, self.instance, tenant = canonicalize(authority_url)
         tenant_discovery_endpoint = (  # Hard code a V2 pattern as default value
             'https://{}/{}/v2.0/.well-known/openid-configuration'
-            .format(WORLD_WIDE, tenant))
+            .format(self.instance, tenant))
         if validate_authority and self.instance not in WELL_KNOWN_AUTHORITY_HOSTS:
             tenant_discovery_endpoint = instance_discovery(
                 canonicalized + "/oauth2/v2.0/authorize",
@@ -46,6 +48,7 @@ def __init__(self, authority_url, validate_authority=True,
         openid_config = tenant_discovery(
             tenant_discovery_endpoint,
             verify=verify, proxies=proxies, timeout=timeout)
+        logger.debug("openid_config = %s", openid_config)
         self.authorization_endpoint = openid_config['authorization_endpoint']
         self.token_endpoint = openid_config['token_endpoint']
         _, _, self.tenant = canonicalize(self.token_endpoint)  # Usually a GUID
@@ -76,7 +79,11 @@ def canonicalize(url):
 def instance_discovery(url, response=None, **kwargs):
     # Returns tenant discovery endpoint
     resp = requests.get(  # Note: This URL seemingly returns V1 endpoint only
-        'https://{}/common/discovery/instance'.format(WORLD_WIDE),
+        'https://{}/common/discovery/instance'.format(
+            WORLD_WIDE  # Historically using WORLD_WIDE. Could use self.instance too
+                # See https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/4.0.0/src/Microsoft.Identity.Client/Instance/AadInstanceDiscovery.cs#L101-L103
+                # and https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/blob/4.0.0/src/Microsoft.Identity.Client/Instance/AadAuthority.cs#L19-L33
+            ),
         params={'authorization_endpoint': url, 'api-version': '1.0'},
         **kwargs)
     payload = response or resp.json()
diff --git a/tests/test_authority.py b/tests/test_authority.py
index 41714552..d7fc5cac 100644
--- a/tests/test_authority.py
+++ b/tests/test_authority.py
@@ -4,24 +4,16 @@
 
 
 class TestAuthority(unittest.TestCase):
-    COMMON_AUTH_ENDPOINT = \
-        'https://login.microsoftonline.com/common/oauth2/v2.0/authorize'
-    COMMON_TOKEN_ENDPOINT = \
-        'https://login.microsoftonline.com/common/oauth2/v2.0/token'
 
     def test_wellknown_host_and_tenant(self):
-        # Test one specific sample in straightforward way, for readability
-        a = Authority('https://login.microsoftonline.com/common')
-        self.assertEqual(a.authorization_endpoint, self.COMMON_AUTH_ENDPOINT)
-        self.assertEqual(a.token_endpoint, self.COMMON_TOKEN_ENDPOINT)
-
-        # Test all well known authority hosts, using same real "common" tenant
+        # Assert all well known authority hosts are using their own "common" tenant
         for host in WELL_KNOWN_AUTHORITY_HOSTS:
             a = Authority('https://{}/common'.format(host))
-            # Note: this "common" tenant endpoints always point to its real host
             self.assertEqual(
-                a.authorization_endpoint, self.COMMON_AUTH_ENDPOINT)
-            self.assertEqual(a.token_endpoint, self.COMMON_TOKEN_ENDPOINT)
+                a.authorization_endpoint,
+                'https://%s/common/oauth2/v2.0/authorize' % host)
+            self.assertEqual(
+                a.token_endpoint, 'https://%s/common/oauth2/v2.0/token' % host)
 
     @unittest.skip("As of Jan 2017, the server no longer returns V1 endpoint")
     def test_lessknown_host_will_return_a_set_of_v1_endpoints(self):
@@ -33,20 +25,12 @@ def test_lessknown_host_will_return_a_set_of_v1_endpoints(self):
         self.assertEqual(a.token_endpoint, v1_token_endpoint)
         self.assertNotIn('v2.0', a.token_endpoint)
 
-    def test_unknown_host(self):
+    def test_unknown_host_wont_pass_instance_discovery(self):
         with self.assertRaisesRegexp(MsalServiceError, "invalid_instance"):
             Authority('https://unknown.host/tenant_doesnt_matter_in_this_case')
 
-    def test_unknown_host_valid_tenant_and_skip_host_validation(self):
-        # When skipping host (a.k.a. instance) validation,
-        # the Tenant Discovery will always use WORLD_WIDE service as instance,
-        # so, if the tenant happens to exist there, it will find some endpoints.
-        a = Authority('https://incorrect.host/common', validate_authority=False)
-        self.assertEqual(a.authorization_endpoint, self.COMMON_AUTH_ENDPOINT)
-        self.assertEqual(a.token_endpoint, self.COMMON_TOKEN_ENDPOINT)
-
-    def test_unknown_host_unknown_tenant_and_skip_host_validation(self):
-        with self.assertRaisesRegexp(MsalServiceError, "invalid_tenant"):
+    def test_invalid_host_skipping_validation_meets_connection_error_down_the_road(self):
+        with self.assertRaises(requests.exceptions.RequestException):
             Authority('https://unknown.host/invalid', validate_authority=False)