diff --git a/doc/README.makefiles b/doc/README.makefiles
index 86237e3b5f..2b11836424 100644
--- a/doc/README.makefiles
+++ b/doc/README.makefiles
@@ -128,3 +128,9 @@ are included in the bottom line of the makefile with
 Dependencies = $(All_Objects:.o=.d) 
 
 include $(Dependancies)
+
+PLATFORM SUBDIRS OF JRD
+
+Please, forget about jrd/os/* in makefiles! Pretend that all files from
+there are placed in jrd/ itself. A little trick in make.rules will find
+files for your platform automatically.