Inconsistent darwin/mac_os_x symbol bug

It was causing:
lib/qt/qmake.rb:114:in `check_qmake!': undefined method `strip' for nil:NilClass (NoMethodError)

lib/qt/qmake.rb

@@ -95,7 +95,7 @@ module Qt
               %{sudo apt-get install make or sudo yum install make}
             when :freebsd
               %{install /usr/ports/devel/gmake}
-            when :darwin
+            when :mac_os_x
               %{Install XCode, and/or sudo port install make}
             end
           )
@@ -121,7 +121,7 @@ MSG
               <<-MSG
 Install /usr/ports/www/qt4-webkit and /usr/ports/devel/qmake4.
 MSG
-            when :darwin
+            when :mac_os_x
               <<-MSG
 sudo port install qt4-mac (for the patient) or downloading Nokia's pre-built binary
 at http://qt.nokia.com/downloads/