diff --git a/ChangeLog b/ChangeLog
index dadd466266..b89f7df6a0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Nov 28 09:15:50 2005  Hirokazu Yamamoto  <ocean@m2.ccsnet.ne.jp>
+
+	* lib/mkmf.rb (create_makefile): should not change sodir with
+	  dir.gsub!. (bccwin32 failed to install third party exntesions)
+	  [ruby-dev:27834]
+
 Sun Nov 27 05:37:20 2005  Tanaka Akira  <akr@m17n.org>
 
 	* lib/pathname.rb: use File.basename to decompose pathnames.
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 4365cbe579..5afe5017d1 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -1102,7 +1102,7 @@ static:		$(STATIC_LIB)#{$extout ? " install-rb" : ""}
   mfile.print CLEANINGS
   dirs = []
   mfile.print "install: install-so install-rb\n\n"
-  sodir = dir = "$(RUBYARCHDIR)"
+  sodir = (dir = "$(RUBYARCHDIR)").dup
   mfile.print("install-so: #{dir}\n")
   if target
     f = "$(DLLIB)"