Ruby 1.9: force ascii encoding for comparison with utf8 regexp

activesupport/lib/active_support/multibyte/chars.rb

@@ -617,6 +617,8 @@ module ActiveSupport #:nodoc:
         # Replaces all ISO-8859-1 or CP1252 characters by their UTF-8 equivalent resulting in a valid UTF-8 string.
         def tidy_bytes(string)
           string.split(//u).map do |c|
+            c.force_encoding(Encoding::ASCII) if c.respond_to?(:force_encoding)
+
             if !UTF8_PAT.match(c)
               n = c.unpack('C')[0]
               n < 128 ? n.chr :