1 files changed, 1 insertions, 1 deletions
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 4e69f765fb..ae0974670c 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -2019,7 +2019,7 @@ preload = #{defined?($preload) && $preload ? $preload.join(' ') : ''}
   end
 
   def timestamp_file(name, target_prefix = nil)
-    pat = {}
+    pat = {'TARGET_SO_DIR'=>'$(RUBYARCHDIR)'}
     install_dirs.each do |n, d|
       pat[n] = $` if /\$\(target_prefix\)\z/ =~ d
     end