diff --git a/tool/fake.rb b/tool/fake.rb
index 91dfb041c4..9c235f1e3a 100644
--- a/tool/fake.rb
+++ b/tool/fake.rb
@@ -48,7 +48,6 @@ class File
   $builtruby ||= File.join(builddir, config['RUBY_INSTALL_NAME'] + config['EXEEXT'])
   RbConfig.fire_update!("builddir", builddir)
   RbConfig.fire_update!("buildlibdir", builddir)
-  RbConfig.fire_update!("libdir", builddir)
   RbConfig.fire_update!("prefix", $topdir)
   RbConfig.fire_update!("top_srcdir", $top_srcdir ||= top_srcdir)
   RbConfig.fire_update!("extout", $extout)