f5eda6
diff --git a/requests/sessions.py b/requests/sessions.py
f5eda6
index a448bd8..d73d700 100644
f5eda6
--- a/requests/sessions.py
f5eda6
+++ b/requests/sessions.py
f5eda6
@@ -19,7 +19,7 @@ from .cookies import (
f5eda6
 from .models import Request, PreparedRequest, DEFAULT_REDIRECT_LIMIT
f5eda6
 from .hooks import default_hooks, dispatch_hook
f5eda6
 from ._internal_utils import to_native_string
f5eda6
-from .utils import to_key_val_list, default_headers
f5eda6
+from .utils import to_key_val_list, default_headers, DEFAULT_PORTS
f5eda6
 from .exceptions import (
f5eda6
     TooManyRedirects, InvalidSchema, ChunkedEncodingError, ContentDecodingError)
f5eda6
 
f5eda6
@@ -128,8 +128,17 @@ class SessionRedirectMixin(object):
f5eda6
         if (old_parsed.scheme == 'http' and old_parsed.port in (80, None)
f5eda6
                 and new_parsed.scheme == 'https' and new_parsed.port in (443, None)):
f5eda6
             return False
f5eda6
+
f5eda6
+        # Handle default port usage corresponding to scheme.
f5eda6
+        changed_port = old_parsed.port != new_parsed.port
f5eda6
+        changed_scheme = old_parsed.scheme != new_parsed.scheme
f5eda6
+        default_port = (DEFAULT_PORTS.get(old_parsed.scheme, None), None)
f5eda6
+        if (not changed_scheme and old_parsed.port in default_port
f5eda6
+                and new_parsed.port in default_port):
f5eda6
+            return False
f5eda6
+
f5eda6
         # Standard case: root URI must match
f5eda6
-        return old_parsed.port != new_parsed.port or old_parsed.scheme != new_parsed.scheme
f5eda6
+        return changed_port or changed_scheme
f5eda6
 
f5eda6
     def resolve_redirects(self, resp, req, stream=False, timeout=None,
f5eda6
                           verify=True, cert=None, proxies=None, yield_requests=False, **adapter_kwargs):
f5eda6
diff --git a/requests/utils.py b/requests/utils.py
f5eda6
index 0ce7fe1..04145c8 100644
f5eda6
--- a/requests/utils.py
f5eda6
+++ b/requests/utils.py
f5eda6
@@ -38,6 +38,8 @@ NETRC_FILES = ('.netrc', '_netrc')
f5eda6
 
f5eda6
 DEFAULT_CA_BUNDLE_PATH = certs.where()
f5eda6
 
f5eda6
+DEFAULT_PORTS = {'http': 80, 'https': 443}
f5eda6
+
f5eda6
 
f5eda6
 if sys.platform == 'win32':
f5eda6
     # provide a proxy_bypass version on Windows without DNS lookups
f5eda6
diff --git a/tests/test_requests.py b/tests/test_requests.py
f5eda6
index f46561e..f99fdaf 100644
f5eda6
--- a/tests/test_requests.py
f5eda6
+++ b/tests/test_requests.py
f5eda6
@@ -1611,6 +1611,17 @@ class TestRequests:
f5eda6
         s = requests.Session()
f5eda6
         assert s.should_strip_auth('http://example.com:1234/foo', 'https://example.com:4321/bar')
f5eda6
 
f5eda6
+    @pytest.mark.parametrize(
f5eda6
+        'old_uri, new_uri', (
f5eda6
+            ('https://example.com:443/foo', 'https://example.com/bar'),
f5eda6
+            ('http://example.com:80/foo', 'http://example.com/bar'),
f5eda6
+            ('https://example.com/foo', 'https://example.com:443/bar'),
f5eda6
+            ('http://example.com/foo', 'http://example.com:80/bar')
f5eda6
+        ))
f5eda6
+    def test_should_strip_auth_default_port(self, old_uri, new_uri):
f5eda6
+        s = requests.Session()
f5eda6
+        assert not s.should_strip_auth(old_uri, new_uri)
f5eda6
+
f5eda6
     def test_manual_redirect_with_partial_body_read(self, httpbin):
f5eda6
         s = requests.Session()
f5eda6
         r1 = s.get(httpbin('redirect/2'), allow_redirects=False, stream=True)