diff --git a/Library/Homebrew/cmd/doctor.rb b/Library/Homebrew/cmd/doctor.rb
index 377873d16a390f5a35199f39785cb916bb2f293a..7d5a4711aa4978ac4dc78a6783d8e09889d572f1 100644
--- a/Library/Homebrew/cmd/doctor.rb
+++ b/Library/Homebrew/cmd/doctor.rb
@@ -796,7 +796,7 @@ def check_git_status
 end
 
 def check_for_leopard_ssl
-  if MacOS.leopard? and not ENV['GIT_SSL_NO_VERIFY']
+  if MacOS.version == :leopard and not ENV['GIT_SSL_NO_VERIFY']
     <<-EOS.undent
       The version of libcurl provided with Mac OS X Leopard has outdated
       SSL certificates.
diff --git a/Library/Homebrew/compat/compatibility.rb b/Library/Homebrew/compat/compatibility.rb
index a8b6afb70576aef668ba219fdd32b40fa9267304..bbd349249d0e8e93c7c03b394edd51a46a6adce2 100644
--- a/Library/Homebrew/compat/compatibility.rb
+++ b/Library/Homebrew/compat/compatibility.rb
@@ -197,4 +197,23 @@ module MacOS extend self
   def x11_prefix
     X11.prefix
   end
+
+  def leopard?
+    10.5 == MACOS_VERSION
+  end
+
+  def snow_leopard?
+    10.6 <= MACOS_VERSION # Actually Snow Leopard or newer
+  end
+  alias_method :snow_leopard_or_newer?, :snow_leopard?
+
+  def lion?
+    10.7 <= MACOS_VERSION # Actually Lion or newer
+  end
+  alias_method :lion_or_newer?, :lion?
+
+  def mountain_lion?
+    10.8 <= MACOS_VERSION # Actually Mountain Lion or newer
+  end
+  alias_method :mountain_lion_or_newer?, :mountain_lion?
 end
diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
index 43d77f531e25afd4d93ce00c241ba94be09d9482..c35bce9fd11833338f2241d97afbc0e5a952800f 100644
--- a/Library/Homebrew/dependencies.rb
+++ b/Library/Homebrew/dependencies.rb
@@ -63,7 +63,7 @@ private
       # Xcode no longer provides autotools or some other build tools
       Dependency.new(spec.to_s) unless MacOS::Xcode.provides_autotools?
     when :libpng, :freetype, :pixman, :fontconfig, :cairo
-      if MacOS.lion_or_newer?
+      if MacOS.version >= :lion
         MacOS::XQuartz.installed? ? X11Dependency.new(tag) : Dependency.new(spec.to_s)
       else
         X11Dependency.new(tag)
diff --git a/Library/Homebrew/download_strategy.rb b/Library/Homebrew/download_strategy.rb
index d589273eee0118881d944ba994af2cb49943b878..d5da87b9310dac505a68adb326c44ec573c990cb 100644
--- a/Library/Homebrew/download_strategy.rb
+++ b/Library/Homebrew/download_strategy.rb
@@ -261,7 +261,7 @@ class SubversionDownloadStrategy < AbstractDownloadStrategy
     svncommand = target.exist? ? 'up' : 'checkout'
     args = [svn, svncommand]
     # SVN shipped with XCode 3.1.4 can't force a checkout.
-    args << '--force' unless MacOS.leopard? and svn == '/usr/bin/svn'
+    args << '--force' unless MacOS.version == :leopard and svn == '/usr/bin/svn'
     args << url if !target.exist?
     args << target
     args << '-r' << revision if revision
diff --git a/Library/Homebrew/extend/ENV.rb b/Library/Homebrew/extend/ENV.rb
index 436886318fbfaabaae19df9a3f69cc238d44219f..c8952b18642149ecca23c06588c9acb760641dee 100644
--- a/Library/Homebrew/extend/ENV.rb
+++ b/Library/Homebrew/extend/ENV.rb
@@ -9,7 +9,7 @@ module HomebrewEnvExtension
     delete('CLICOLOR_FORCE') # autotools doesn't like this
     remove_cc_etc
 
-    if MacOS.mountain_lion?
+    if MacOS.version >= :mountain_lion
       # Fix issue with sed barfing on unicode characters on Mountain Lion.
       delete('LC_ALL')
       self['LC_CTYPE']="C"
diff --git a/Library/Homebrew/macos.rb b/Library/Homebrew/macos.rb
index 1fd7d928f61e6cb6ab88c2c7295a8d97c7ffa8b8..cee7902423316dcffd8aa1edd16f3a4f78372b7d 100644
--- a/Library/Homebrew/macos.rb
+++ b/Library/Homebrew/macos.rb
@@ -8,16 +8,11 @@ module MacOS extend self
   end
 
   def cat
-    if mountain_lion?
-      :mountainlion
-    elsif lion?
-      :lion
-    elsif snow_leopard?
-      :snowleopard
-    elsif leopard?
-      :leopard
-    else
-      nil
+    if version == :mountain_lion then :mountainlion
+    elsif version == :lion then :lion
+    elsif version == :snow_leopard then :snowleopard
+    elsif version == :leopard then :leopard
+    else nil
     end
   end
 
@@ -200,27 +195,8 @@ module MacOS extend self
     false
   end
 
-  def leopard?
-    10.5 == MACOS_VERSION
-  end
-
-  def snow_leopard?
-    10.6 <= MACOS_VERSION # Actually Snow Leopard or newer
-  end
-  alias :snow_leopard_or_newer? :snow_leopard?
-
-  def lion?
-    10.7 <= MACOS_VERSION # Actually Lion or newer
-  end
-  alias :lion_or_newer? :lion?
-
-  def mountain_lion?
-    10.8 <= MACOS_VERSION # Actually Mountain Lion or newer
-  end
-  alias :mountain_lion_or_newer? :mountain_lion?
-
   def prefer_64_bit?
-    Hardware.is_64_bit? and not leopard?
+    Hardware.is_64_bit? and version != :leopard
   end
 
   StandardCompilers = {