diff --git a/ChangeLog b/ChangeLog
index a9987cc284..1e2df052db 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Aug 24 15:42:28 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/mkmf.rb (create_makefile): use timestamp for destination
+	  directories.  [ruby-dev:46067] [Bug #6904]
+
 Fri Aug 24 12:40:15 2012  Luis Lavena  <luislavena@gmail.com>
 
 	* configure.in (mingw): add shlwapi to the list of dependency
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index cb3adbad03..d3c758a038 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -1831,6 +1831,7 @@ INSTALL = #{config_string('INSTALL', &possible_command) || '@$(RUBY) -run -e ins
 INSTALL_PROG = #{config_string('INSTALL_PROG') || '$(INSTALL) -m 0755'}
 INSTALL_DATA = #{config_string('INSTALL_DATA') || '$(INSTALL) -m 0644'}
 COPY = #{config_string('CP', &possible_command) || '@$(RUBY) -run -e cp -- -v'}
+TOUCH = exit >
 
 #### End of system configuration section. ####
 
@@ -1847,6 +1848,11 @@ preload = #{defined?($preload) && $preload ? $preload.join(' ') : ''}
     end
     mk
   end
+
+  def timestamp_file(name)
+    name = name.gsub(/(\$[({]|[})])|(\/+)|[^-.\w]+/) {$1 ? "@" : $2 ? "%" : "_"}
+    "./.#{name}.time"
+  end
   # :startdoc:
 
   # creates a stub Makefile.
@@ -2142,7 +2148,7 @@ static: $(STATIC_LIB)#{$extout ? " install-rb" : ""}
       for dir, *files in files
         unless dirs.include?(dir)
           dirs << dir
-          mfile.print "pre-install-rb#{sfx}: #{dir}\n"
+          mfile.print "pre-install-rb#{sfx}: #{timestamp_file(dir)}\n"
         end
         for f in files
           dest = "#{dir}/#{File.basename(f)}"
@@ -2171,7 +2177,10 @@ static: $(STATIC_LIB)#{$extout ? " install-rb" : ""}
       end
     end
     dirs.unshift(sodir) if target and !dirs.include?(sodir)
-    dirs.each {|d| mfile.print "#{d}:\n\t$(Q) $(MAKEDIRS) $@\n"}
+    dirs.each do |d|
+      t = timestamp_file(d)
+      mfile.print "#{t}:\n\t$(Q) $(MAKEDIRS) #{d}\n\t$(Q) $(TOUCH) $@\n"
+    end
 
     mfile.print <<-SITEINSTALL
 
@@ -2204,10 +2213,11 @@ site-install-rb: install-rb
     mfile.print "$(RUBYARCHDIR)/" if $extout
     mfile.print "$(DLLIB): "
     mfile.print "$(DEFFILE) " if makedef
-    mfile.print "$(OBJS) Makefile\n"
+    mfile.print "$(OBJS) Makefile"
+    mfile.print " #{timestamp_file('$(RUBYARCHDIR)')}\n" if $extout
+    mfile.print "\n"
     mfile.print "\t$(ECHO) linking shared-object #{target_prefix.sub(/\A\/(.*)/, '\1/')}$(DLLIB)\n"
     mfile.print "\t-$(Q)$(RM) $(@#{sep})\n"
-    mfile.print "\t-$(Q)$(MAKEDIRS) $(@D)\n" if $extout
     link_so = LINK_SO.gsub(/^/, "\t$(Q) ")
     if srcs.any?(&%r"\.(?:#{CXX_EXT.join('|')})\z".method(:===))
       link_so = link_so.sub(/\bLDSHARED\b/, '\&XX')