diff --git a/lib/mruby/core_ext.rb b/lib/mruby/core_ext.rb
index c404bfec9..33454edad 100644
--- a/lib/mruby/core_ext.rb
+++ b/lib/mruby/core_ext.rb
@@ -21,6 +21,7 @@ class String
 end
 
 def install_D(src, dst)
+  _pp "INSTALL", src.relative_path, dst.relative_path
   rm_f dst
   mkdir_p File.dirname(dst)
   cp src, dst