diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 0259770..2994ad9 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -11,6 +11,7 @@ This project adheres to `Semantic Versioning`_.
 - Fixed issue where UnboundLocalError would be raised during COT's
   attempt to clean up after a qemu-img error occurring while trying to
   convert a disk to VMDK (`#67`_).
+- Fixed incorrect invocation of 'sudo mkdir' on Mac OS X.
 
 `2.0.2`_ - 2017-03-20
 ---------------------
diff --git a/COT/helpers/helper.py b/COT/helpers/helper.py
index 8750f2a..57a9d78 100644
--- a/COT/helpers/helper.py
+++ b/COT/helpers/helper.py
@@ -466,7 +466,8 @@ def mkdir(directory, permissions=493):    # 493 == 0o755
                          directory)
             try:
                 check_call(['sudo', 'mkdir', '-p',
-                            '--mode=%o' % permissions,
+                            # We previously used '--mode' but OS X lacks it.
+                            '-m', '%o' % permissions,
                             directory])
             except HelperError:
                 # That failed too - re-raise the original exception
@@ -588,7 +589,8 @@ def check_call(args, require_success=True, retry_with_sudo=False, **kwargs):
         # to:
         # ENOEXEC "Exec format error"
         # We shouldn't see ENOEXEC otherwise, so we special case this.
-        if exc.errno == errno.ENOEXEC and args[0] == 'sudo': # pragma: no cover
+        if (exc.errno == errno.ENOEXEC and    # pragma: no cover
+                args[0] == 'sudo'):
             raise HelperError(exc.errno, "The 'sudo' command is unavailable")
         if exc.errno != errno.ENOENT:
             raise
diff --git a/COT/helpers/tests/test_fatdisk.py b/COT/helpers/tests/test_fatdisk.py
index 5914636..fd94407 100644
--- a/COT/helpers/tests/test_fatdisk.py
+++ b/COT/helpers/tests/test_fatdisk.py
@@ -92,7 +92,7 @@ def test_install_apt_get(self,
                 ['apt-get', '-q', 'install', 'make'],
                 ['apt-get', '-q', 'install', 'gcc'],
                 ['./RUNME'],
-                ['sudo', 'mkdir', '-p', '--mode=755', '/usr/local/bin'],
+                ['sudo', 'mkdir', '-p', '-m', '755', '/usr/local/bin'],
             ])
         self.assertTrue(re.search("/fatdisk$", mock_copy.call_args[0][0]))
         self.assertEqual('/usr/local/bin', mock_copy.call_args[0][1])
@@ -119,7 +119,7 @@ def test_install_apt_get(self,
             mock_check_call,
             [
                 ['./RUNME'],
-                ['sudo', 'mkdir', '-p', '--mode=755',
+                ['sudo', 'mkdir', '-p', '-m', '755',
                  '/home/cot/opt/local/bin'],
             ])
         self.assertTrue(re.search("/fatdisk$", mock_copy.call_args[0][0]))
@@ -156,7 +156,7 @@ def test_install_yum(self,
                 ['yum', '--quiet', 'install', 'make'],
                 ['yum', '--quiet', 'install', 'gcc'],
                 ['./RUNME'],
-                ['sudo', 'mkdir', '-p', '--mode=755', '/usr/local/bin'],
+                ['sudo', 'mkdir', '-p', '-m', '755', '/usr/local/bin'],
             ])
         self.assertTrue(re.search("/fatdisk$", mock_copy.call_args[0][0]))
         self.assertEqual('/usr/local/bin', mock_copy.call_args[0][1])
diff --git a/COT/helpers/tests/test_helper.py b/COT/helpers/tests/test_helper.py
index 4d7f047..ec889a9 100644
--- a/COT/helpers/tests/test_helper.py
+++ b/COT/helpers/tests/test_helper.py
@@ -500,7 +500,7 @@ def test_need_sudo(self, mock_isdir, mock_exists,
         mock_exists.assert_called_with('/foo/bar')
         mock_makedirs.assert_called_with('/foo/bar', 493)  # 493 == 0o755
         mock_check_call.assert_called_with(
-            ['sudo', 'mkdir', '-p', '--mode=755', '/foo/bar'])
+            ['sudo', 'mkdir', '-p', '-m', '755', '/foo/bar'])
 
     def test_nondefault_permissions(self, mock_isdir, mock_exists,
                                     mock_makedirs, mock_check_call):
@@ -518,7 +518,7 @@ def test_nondefault_permissions(self, mock_isdir, mock_exists,
         self.assertTrue(Helper.mkdir('/foo/bar', 511))  # 511 == 0o777
         mock_makedirs.assert_called_with('/foo/bar', 511)
         mock_check_call.assert_called_with(
-            ['sudo', 'mkdir', '-p', '--mode=777', '/foo/bar'])
+            ['sudo', 'mkdir', '-p', '-m', '777', '/foo/bar'])
 
 
 @mock.patch('COT.helpers.helper.check_call')
diff --git a/COT/helpers/tests/test_vmdktool.py b/COT/helpers/tests/test_vmdktool.py
index 9e04aab..357a1e4 100644
--- a/COT/helpers/tests/test_vmdktool.py
+++ b/COT/helpers/tests/test_vmdktool.py
@@ -84,8 +84,8 @@ def test_install_helper_apt_get(self,
                 ['apt-get', '-q', 'install', 'make'],
                 ['apt-get', '-q', 'install', 'zlib1g-dev'],
                 ['make', 'CFLAGS="-D_GNU_SOURCE -g -O -pipe"'],
-                ['sudo', 'mkdir', '-p', '--mode=755', '/usr/local/man/man8'],
-                ['sudo', 'mkdir', '-p', '--mode=755', '/usr/local/bin'],
+                ['sudo', 'mkdir', '-p', '-m', '755', '/usr/local/man/man8'],
+                ['sudo', 'mkdir', '-p', '-m', '755', '/usr/local/bin'],
                 ['make', 'install', 'PREFIX=/usr/local'],
             ])
         self.assertAptUpdated()
@@ -111,9 +111,9 @@ def test_install_helper_apt_get(self,
             mock_check_call,
             [
                 ['make', 'CFLAGS="-D_GNU_SOURCE -g -O -pipe"'],
-                ['sudo', 'mkdir', '-p', '--mode=755',
+                ['sudo', 'mkdir', '-p', '-m', '755',
                  '/home/cot/opt/local/man/man8'],
-                ['sudo', 'mkdir', '-p', '--mode=755',
+                ['sudo', 'mkdir', '-p', '-m', '755',
                  '/home/cot/opt/local/bin'],
                 ['make', 'install', 'PREFIX=/opt/local', 'DESTDIR=/home/cot'],
             ])
@@ -146,8 +146,8 @@ def test_install_helper_yum(self,
                 ['yum', '--quiet', 'install', 'make'],
                 ['yum', '--quiet', 'install', 'zlib-devel'],
                 ['make', 'CFLAGS="-D_GNU_SOURCE -g -O -pipe"'],
-                ['sudo', 'mkdir', '-p', '--mode=755', '/usr/local/man/man8'],
-                ['sudo', 'mkdir', '-p', '--mode=755', '/usr/local/bin'],
+                ['sudo', 'mkdir', '-p', '-m', '755', '/usr/local/man/man8'],
+                ['sudo', 'mkdir', '-p', '-m', '755', '/usr/local/bin'],
                 ['make', 'install', 'PREFIX=/usr/local'],
             ])