diff --git a/Lib/distutils/spawn.py b/Lib/distutils/spawn.py
index 0d1bd0391e6f11..f50edd2da97100 100644
--- a/Lib/distutils/spawn.py
+++ b/Lib/distutils/spawn.py
@@ -54,8 +54,8 @@ def spawn(cmd, search_path=1, verbose=0, dry_run=0):
         global _cfg_target, _cfg_target_split
         if _cfg_target is None:
             from distutils import sysconfig
-            _cfg_target = sysconfig.get_config_var(
-                                  'MACOSX_DEPLOYMENT_TARGET') or ''
+            _cfg_target = str(sysconfig.get_config_var(
+                                  'MACOSX_DEPLOYMENT_TARGET') or '')
             if _cfg_target:
                 _cfg_target_split = [int(x) for x in _cfg_target.split('.')]
         if _cfg_target:
diff --git a/Lib/distutils/tests/test_build_ext.py b/Lib/distutils/tests/test_build_ext.py
index 6bb009a86f41eb..a3055c19840326 100644
--- a/Lib/distutils/tests/test_build_ext.py
+++ b/Lib/distutils/tests/test_build_ext.py
@@ -456,7 +456,7 @@ def test_deployment_target_higher_ok(self):
         deptarget = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
         if deptarget:
             # increment the minor version number (i.e. 10.6 -> 10.7)
-            deptarget = [int(x) for x in deptarget.split('.')]
+            deptarget = [int(x) for x in str(deptarget).split('.')]
             deptarget[-1] += 1
             deptarget = '.'.join(str(i) for i in deptarget)
             self._try_compile_deployment_target('<', deptarget)
@@ -489,7 +489,7 @@ def _try_compile_deployment_target(self, operator, target):
 
         # get the deployment target that the interpreter was built with
         target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
-        target = tuple(map(int, target.split('.')[0:2]))
+        target = tuple(map(int, str(target).split('.')[0:2]))
         # format the target value as defined in the Apple
         # Availability Macros.  We can't use the macro names since
         # at least one value we test with will not exist yet.
@@ -498,7 +498,11 @@ def _try_compile_deployment_target(self, operator, target):
             target = '%02d%01d0' % target
         else:
             # for 10.10 and beyond -> "10nn00"
-            target = '%02d%02d00' % target
+            if len(target) >= 2:
+                target = '%02d%02d00' % target
+            else:
+                # 11 and later can have no minor version (11 instead of 11.0)
+                target = '%02d0000' % target
         deptarget_ext = Extension(
             'deptarget',
             [deptarget_c],
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index a522717751ac17..7a112ef724091f 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1056,7 +1056,7 @@ def test_getgroups(self):
         if sys.platform == 'darwin':
             import sysconfig
             dt = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET') or '10.0'
-            if tuple(int(n) for n in dt.split('.')[0:2]) < (10, 6):
+            if tuple(int(n) for n in str(dt).split('.')[0:2]) < (10, 6):
                 raise unittest.SkipTest("getgroups(2) is broken prior to 10.6")
 
         # 'id -G' and 'os.getgroups()' should return the same
diff --git a/Misc/NEWS.d/next/macOS/2020-12-02-15-48-40.bpo-42504.RQmMOR.rst b/Misc/NEWS.d/next/macOS/2020-12-02-15-48-40.bpo-42504.RQmMOR.rst
new file mode 100644
index 00000000000000..c83bc2b9eeec5f
--- /dev/null
+++ b/Misc/NEWS.d/next/macOS/2020-12-02-15-48-40.bpo-42504.RQmMOR.rst
@@ -0,0 +1 @@
+Fix build on macOS Big Sur when MACOSX_DEPLOYMENT_TARGET=11
\ No newline at end of file
diff --git a/setup.py b/setup.py
index b7a7d26c5325bc..0c9a4250168692 100644
--- a/setup.py
+++ b/setup.py
@@ -1014,7 +1014,7 @@ def detect_readline_curses(self):
             os_release = int(os.uname()[2].split('.')[0])
             dep_target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
             if (dep_target and
-                    (tuple(int(n) for n in dep_target.split('.')[0:2])
+                    (tuple(int(n) for n in str(dep_target).split('.')[0:2])
                         < (10, 5) ) ):
                 os_release = 8
             if os_release < 9: