diff --git a/make_helpers/windows.mk b/make_helpers/windows.mk
index c4317d5..5138d1b 100644
--- a/make_helpers/windows.mk
+++ b/make_helpers/windows.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are met:
@@ -75,12 +75,15 @@
 
     # ${1} is the directory to be generated.
     # ${2} is optional, and allows prerequisites to be specified.
+    # Do nothing if $1 == $2, to ignore self dependencies.
     define MAKE_PREREQ_DIR
+        ifneq (${1},${2})
 
 ${1} : ${2}
 	$(eval tmp_dir:=$(subst /,\,${1}))
 	-@if not exist "$(tmp_dir)"  mkdir "${tmp_dir}"
 
+        endif
     endef
 
     # ${1} is the directory to be removed.