diff --git a/ChangeLog b/ChangeLog
index f8fe1307a3..0121237541 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Apr 20 16:52:20 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* too/fake.rb: don't fake libdir.  use libdirname instead.
+
 Mon Apr 20 16:49:52 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* lib/mkmf.rb (MakeMakefile#configuration): DESTDIR should never affect
diff --git a/tool/fake.rb b/tool/fake.rb
index 0a8e25036a..f8c68173e6 100644
--- a/tool/fake.rb
+++ b/tool/fake.rb
@@ -24,7 +24,7 @@ prehook = proc do |extmk|
     mkconfig["builddir"] = config["builddir"] = builddir
     config["rubyhdrdir"] = File.join(mkconfig["top_srcdir"], "include")
     config["rubyarchhdrdir"] = File.join(builddir, config["EXTOUT"], "include", config["arch"])
-    mkconfig["libdir"] = config["libdir"] = mkconfig["topdir"]
+    mkconfig["libdirname"] = "builddir"
     trace_var(:$ruby, posthook)
   end
   untrace_var(:$extmk, prehook)