diff --git a/lib/spack/spack/operating_systems/mac_osx.py b/lib/spack/spack/operating_systems/mac_os.py
similarity index 53%
rename from lib/spack/spack/operating_systems/mac_osx.py
rename to lib/spack/spack/operating_systems/mac_os.py
index 3cf9b4e12e..f35b3ca577 100644
--- a/lib/spack/spack/operating_systems/mac_osx.py
+++ b/lib/spack/spack/operating_systems/mac_os.py
@@ -1,28 +1,29 @@
 import platform as py_platform
 from spack.architecture import OperatingSystem
 
-class MacOsx(OperatingSystem):
-    """ This class represents the MAC_OSX operating system. This will be auto
-    detected using the python platform.mac_ver. The MAC_OSX platform
-    will be represented using the major version operating system name, i.e
-    el capitan, yosemite...etc.
+class MacOs(OperatingSystem):
+    """This class represents the macOS operating system. This will be
+    auto detected using the python platform.mac_ver. The macOS
+    platform will be represented using the major version operating
+    system name, i.e el capitan, yosemite...etc.
     """
-    
+
     def __init__(self):
         """ Autodetects the mac version from a dictionary. Goes back as
             far as 10.6 snowleopard. If the user has an older mac then
             the version will just be a generic mac_os.
         """
-        mac_releases = {'10.6': "snowleopard", 
+        mac_releases = {'10.6': "snowleopard",
                         "10.7": "lion",
                         "10.8": "mountainlion",
                         "10.9": "mavericks",
                         "10.10": "yosemite",
-                        "10.11": "elcapitan"}     
+                        "10.11": "elcapitan",
+                        "10.12": "sierra"}
 
         mac_ver = py_platform.mac_ver()[0][:-2]
-        name = mac_releases.get(mac_ver, "mac_osx")
-        super(MacOsx, self).__init__(name, mac_ver)
+        name = mac_releases.get(mac_ver, "macos")
+        super(MacOs, self).__init__(name, mac_ver)
 
     def __str__(self):
         return self.name
diff --git a/lib/spack/spack/platforms/darwin.py b/lib/spack/spack/platforms/darwin.py
index 8c8af83d55..d47dd640f9 100644
--- a/lib/spack/spack/platforms/darwin.py
+++ b/lib/spack/spack/platforms/darwin.py
@@ -1,6 +1,6 @@
 import subprocess
 from spack.architecture import Platform, Target
-from spack.operating_systems.mac_osx import MacOsx
+from spack.operating_systems.mac_os import MacOs
 
 class Darwin(Platform):
     priority    = 89
@@ -11,8 +11,8 @@ class Darwin(Platform):
     def __init__(self):
         super(Darwin, self).__init__('darwin')
         self.add_target(self.default, Target(self.default))
-        mac_os = MacOsx()
-        
+        mac_os = MacOs()
+
         self.default_os = str(mac_os)
         self.front_os   = str(mac_os)
         self.back_os    = str(mac_os)
diff --git a/lib/spack/spack/test/operating_system.py b/lib/spack/spack/test/operating_system.py
index 205408db3f..ed5f6ff8ad 100644
--- a/lib/spack/spack/test/operating_system.py
+++ b/lib/spack/spack/test/operating_system.py
@@ -10,7 +10,7 @@
 from spack.platforms.linux import Linux
 from spack.platforms.darwin import Darwin
 from spack.operating_system.linux_distro import LinuxDistro
-from spack.operating_system.mac_osx import MacOSX
+from spack.operating_system.mac_os import MacOs
 from spack.operating_system.cnl import ComputeNodeLinux
 
 class TestOperatingSystem(unittest.TestCase):
@@ -27,12 +27,12 @@ def setUp(self):
 
     def test_cray_front_end_operating_system(self):
         self.assertIsInstance(self.cray_operating_sys, LinuxDistro)
-    
+
     def test_cray_front_end_compiler_strategy(self):
         self.assertEquals(self.cray_operating_sys.compiler_strategy, "PATH")
 
     def test_cray_back_end_operating_system(self):
-        self.assertIsInstance(self.cray_back_os,ComputeNodeLinux) 
+        self.assertIsInstance(self.cray_back_os,ComputeNodeLinux)
 
     def test_cray_back_end_compiler_strategy(self):
         self.assertEquals(self.cray_back_os.compiler_strategy, "MODULES")
@@ -43,16 +43,13 @@ def test_linux_operating_system(self):
     def test_linux_compiler_strategy(self):
         self.assertEquals(self.linux_operating_sys.compiler_strategy, "PATH")
 
-    
+
     def test_cray_front_end_compiler_list(self):
         """ Operating systems will now be in charge of finding compilers.
             So, depending on which operating system you want to build for
-            or which operating system you are on, then you could detect 
+            or which operating system you are on, then you could detect
             compilers in a certain way. Cray linux environment on the front
             end is just a regular linux distro whereas the Cray linux compute
             node is a stripped down version which modules are important
         """
         self.assertEquals(True, False)
-
-
-