diff --git a/Lib/distutils/sysconfig.py b/Lib/distutils/sysconfig.py
index 0c726d9..4aa9334 100644
--- a/Lib/distutils/sysconfig.py
+++ b/Lib/distutils/sysconfig.py
@@ -175,9 +175,15 @@
                             'CCSHARED', 'LDSHARED', 'SO', 'AR',
                             'ARFLAGS')
 
-        newcc = None
         if 'CC' in os.environ:
-            cc = os.environ['CC']
+            newcc = os.environ['CC']
+            if (sys.platform == 'darwin'
+                    and 'LDSHARED' not in os.environ
+                    and ldshared.startswith(cc)):
+                # On OS X, if CC is overridden, use that as the default
+                #       command for LDSHARED as well
+                ldshared = newcc + ldshared[len(cc):]
+            cc = newcc
         if 'CXX' in os.environ:
             cxx = os.environ['CXX']
         if 'LDSHARED' in os.environ:
diff --git a/Lib/distutils/tests/test_unixccompiler.py b/Lib/distutils/tests/test_unixccompiler.py
index 40c908a..64f9d26 100644
--- a/Lib/distutils/tests/test_unixccompiler.py
+++ b/Lib/distutils/tests/test_unixccompiler.py
@@ -1,7 +1,8 @@
 """Tests for distutils.unixccompiler."""
+import os
 import sys
 import unittest
-from test.test_support import run_unittest
+from test.test_support import EnvironmentVarGuard, run_unittest
 
 from distutils import sysconfig
 from distutils.unixccompiler import UnixCCompiler
@@ -122,6 +123,37 @@
         sysconfig.get_config_var = gcv
         self.assertEqual(self.cc.rpath_foo(), '-R/foo')
 
+    @unittest.skipUnless(sys.platform == 'darwin', 'test only relevant for OS X')
+    def test_osx_cc_overrides_ldshared(self):
+        # Issue #18080:
+        # ensure that setting CC env variable also changes default linker
+        def gcv(v):
+            if v == 'LDSHARED':
+                return 'gcc-4.2 -bundle -undefined dynamic_lookup '
+            return 'gcc-4.2'
+        sysconfig.get_config_var = gcv
+        with EnvironmentVarGuard() as env:
+            env['CC'] = 'my_cc'
+            del env['LDSHARED']
+            sysconfig.customize_compiler(self.cc)
+        self.assertEqual(self.cc.linker_so[0], 'my_cc')
+
+    @unittest.skipUnless(sys.platform == 'darwin', 'test only relevant for OS X')
+    def test_osx_explict_ldshared(self):
+        # Issue #18080:
+        # ensure that setting CC env variable does not change
+        #   explicit LDSHARED setting for linker
+        def gcv(v):
+            if v == 'LDSHARED':
+                return 'gcc-4.2 -bundle -undefined dynamic_lookup '
+            return 'gcc-4.2'
+        sysconfig.get_config_var = gcv
+        with EnvironmentVarGuard() as env:
+            env['CC'] = 'my_cc'
+            env['LDSHARED'] = 'my_ld -bundle -dynamic'
+            sysconfig.customize_compiler(self.cc)
+        self.assertEqual(self.cc.linker_so[0], 'my_ld')
+
 
 def test_suite():
     return unittest.makeSuite(UnixCCompilerTestCase)