diff --git a/lib/minitest/unit.rb b/lib/minitest/unit.rb
index 141f9690..6f734037 100644
--- a/lib/minitest/unit.rb
+++ b/lib/minitest/unit.rb
@@ -61,14 +61,12 @@ def UNDEFINED.inspect # :nodoc:
       "UNDEFINED" # again with the rdoc bugs... :(
     end
 
-    WINDOZE = RbConfig::CONFIG['host_os'] =~ /mswin|mingw/ # :nodoc:
-
     ##
     # Returns the diff command to use in #diff. Tries to intelligently
     # figure out what diff to use.
 
     def self.diff
-      @diff = if WINDOZE
+      @diff = if RbConfig::CONFIG['host_os'] =~ /mswin|mingw/ then
                 "diff.exe -u"
               else
                 if system("gdiff", __FILE__, __FILE__)