diff --git a/make_helpers/unix.mk b/make_helpers/unix.mk
index ab60435..6f70200 100644
--- a/make_helpers/unix.mk
+++ b/make_helpers/unix.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:
@@ -67,11 +67,14 @@
 
     # ${1} is the directory to be generated.
     # ${2} is optional, and allows a prerequisite to be specified.
+    # Do nothing if $1 == $2, to ignore self dependencies.
     define MAKE_PREREQ_DIR
+        ifneq (${1},${2})
 
 ${1} : ${2}
 	${Q}mkdir -p  "${1}"
 
+        endif
     endef
 
     define SHELL_REMOVE_DIR