diff --git a/vendor/rails/actionpack/lib/action_controller/vendor/rack-1.1.pre/rack/rewindable_input.rb b/vendor/rails/actionpack/lib/action_controller/vendor/rack-1.1.pre/rack/rewindable_input.rb
index 2347dc35..2864d510 100644
--- a/vendor/rails/actionpack/lib/action_controller/vendor/rack-1.1.pre/rack/rewindable_input.rb
+++ b/vendor/rails/actionpack/lib/action_controller/vendor/rack-1.1.pre/rack/rewindable_input.rb
@@ -72,7 +72,7 @@ module Rack
       # access it because we have the file handle open.
       @rewindable_io = Tempfile.new('RackRewindableInput')
       @rewindable_io.chmod(0000)
-      if filesystem_has_posix_semantics?
+      if filesystem_has_posix_semantics? && !tempfile_unlink_contains_bug?
         @rewindable_io.unlink
         @unlinked = true
       end
@@ -94,5 +94,15 @@ module Rack
     def filesystem_has_posix_semantics?
       RUBY_PLATFORM !~ /(mswin|mingw|cygwin|java)/
     end
+
+    def tempfile_unlink_contains_bug?
+      # The tempfile library as included in Ruby 1.9.1-p152 and later
+      # contains a bug: unlinking an open Tempfile object also closes
+      # it, which breaks our expected POSIX semantics. This problem
+      # has been fixed in Ruby 1.9.2, but the Ruby team chose not to
+      # include the bug fix in later versions of the 1.9.1 series.
+      ruby_engine = defined?(RUBY_ENGINE) ? RUBY_ENGINE : "ruby"
+      ruby_engine == "ruby" && RUBY_VERSION == "1.9.1" && RUBY_PATCHLEVEL >= 152
+    end
   end
 end