diff --git a/test/mkmf/base.rb b/test/mkmf/base.rb
index dbaf666887..d8e2a04fe7 100644
--- a/test/mkmf/base.rb
+++ b/test/mkmf/base.rb
@@ -49,7 +49,11 @@ module TestMkmf::Base
       @filter = block
     end
     def write(s)
-      @buffer << s if @out
+      if @out
+        @buffer << s
+      elsif @origin
+        @origin << s
+      end
     end
   end