diff --git a/src/wheel/macosx_libfile.py b/src/wheel/macosx_libfile.py
index 9141f269..f8ad3cab 100644
--- a/src/wheel/macosx_libfile.py
+++ b/src/wheel/macosx_libfile.py
@@ -350,15 +350,16 @@ def calculate_macosx_platform_tag(archive_root, platform_tag):
     """
     prefix, base_version, suffix = platform_tag.split('-')
     base_version = tuple([int(x) for x in base_version.split(".")])
-    if len(base_version) >= 2:
-        base_version = base_version[0:2]
-
+    base_version = base_version[:2]
+    if base_version[0] > 10:
+        base_version = (base_version[0], 0)
     assert len(base_version) == 2
     if "MACOSX_DEPLOYMENT_TARGET" in os.environ:
         deploy_target = tuple([int(x) for x in os.environ[
             "MACOSX_DEPLOYMENT_TARGET"].split(".")])
-        if len(deploy_target) >= 2:
-            deploy_target = deploy_target[0:2]
+        deploy_target = deploy_target[:2]
+        if deploy_target[0] > 10:
+            deploy_target = (deploy_target[0], 0)
         if deploy_target < base_version:
             sys.stderr.write(
                  "[WARNING] MACOSX_DEPLOYMENT_TARGET is set to a lower value ({}) than the "
@@ -378,7 +379,10 @@ def calculate_macosx_platform_tag(archive_root, platform_tag):
                 lib_path = os.path.join(dirpath, filename)
                 min_ver = extract_macosx_min_system_version(lib_path)
                 if min_ver is not None:
-                    versions_dict[lib_path] = min_ver[0:2]
+                    min_ver = min_ver[0:2]
+                    if min_ver[0] > 10:
+                        min_ver = (min_ver[0], 0)
+                    versions_dict[lib_path] = min_ver
 
     if len(versions_dict) > 0:
         base_version = max(base_version, max(versions_dict.values()))
diff --git a/tests/test_macosx_libfile.py b/tests/test_macosx_libfile.py
index 35cff83b..337f0e30 100644
--- a/tests/test_macosx_libfile.py
+++ b/tests/test_macosx_libfile.py
@@ -21,7 +21,8 @@ def test_read_from_dylib():
         ("test_lib_10_10_386.dylib", "10.10.0"),
         ("test_lib_10_14_386.dylib", "10.14.0"),
         ("test_lib_multiple_fat.dylib", "10.14.0"),
-        ("test_lib_10_10_10.dylib", "10.10.10")
+        ("test_lib_10_10_10.dylib", "10.10.10"),
+        ("test_lib_11.dylib", "11.0.0"),
     ]
     for file_name, ver in versions:
         extracted = extract_macosx_min_system_version(
@@ -48,14 +49,14 @@ class TestGetPlatformMacosx:
     def test_simple(self, monkeypatch):
         dirname = os.path.dirname(__file__)
         dylib_dir = os.path.join(dirname, "testdata", "macosx_minimal_system_version")
-        monkeypatch.setattr(distutils.util, "get_platform", return_factory("macosx-10.14-x86_64"))
-        assert get_platform(dylib_dir) == "macosx_10_14_x86_64"
+        monkeypatch.setattr(distutils.util, "get_platform", return_factory("macosx-11.0-x86_64"))
+        assert get_platform(dylib_dir) == "macosx_11_0_x86_64"
 
     def test_version_bump(self, monkeypatch, capsys):
         dirname = os.path.dirname(__file__)
         dylib_dir = os.path.join(dirname, "testdata", "macosx_minimal_system_version")
         monkeypatch.setattr(distutils.util, "get_platform", return_factory("macosx-10.9-x86_64"))
-        assert get_platform(dylib_dir) == "macosx_10_14_x86_64"
+        assert get_platform(dylib_dir) == "macosx_11_0_x86_64"
         captured = capsys.readouterr()
         assert "[WARNING] This wheel needs a higher macOS version than" in captured.err
 
@@ -127,6 +128,25 @@ def test_warning_on_to_low_env_variable(self, monkeypatch, capsys):
         captured = capsys.readouterr()
         assert "MACOSX_DEPLOYMENT_TARGET is set to a lower value (10.8) than the" in captured.err
 
+    def test_get_platform_bigsur_env(self, monkeypatch):
+        dirname = os.path.dirname(__file__)
+        dylib_dir = os.path.join(dirname, "testdata", "macosx_minimal_system_version")
+        monkeypatch.setattr(distutils.util, "get_platform", return_factory("macosx-10.9-x86_64"))
+        monkeypatch.setenv("MACOSX_DEPLOYMENT_TARGET", "11")
+        monkeypatch.setattr(os, "walk", return_factory(
+            [(dylib_dir, [], ["test_lib_10_6.dylib", "test_lib_10_10_fat.dylib"])]
+        ))
+        assert get_platform(dylib_dir) == "macosx_11_0_x86_64"
+
+    def test_get_platform_bigsur_platform(self, monkeypatch):
+        dirname = os.path.dirname(__file__)
+        dylib_dir = os.path.join(dirname, "testdata", "macosx_minimal_system_version")
+        monkeypatch.setattr(distutils.util, "get_platform", return_factory("macosx-11-x86_64"))
+        monkeypatch.setattr(os, "walk", return_factory(
+            [(dylib_dir, [], ["test_lib_10_6.dylib", "test_lib_10_10_fat.dylib"])]
+        ))
+        assert get_platform(dylib_dir) == "macosx_11_0_x86_64"
+
 
 def test_get_platform_linux(monkeypatch):
     monkeypatch.setattr(distutils.util, "get_platform", return_factory("linux_x86_64"))
diff --git a/tests/testdata/macosx_minimal_system_version/test_lib_11.dylib b/tests/testdata/macosx_minimal_system_version/test_lib_11.dylib
new file mode 100644
index 00000000..80202c11
Binary files /dev/null and b/tests/testdata/macosx_minimal_system_version/test_lib_11.dylib differ