diff --git a/make_helpers/tbbr/tbbr_tools.mk b/make_helpers/tbbr/tbbr_tools.mk
index afc007a..9c47cc7 100644
--- a/make_helpers/tbbr/tbbr_tools.mk
+++ b/make_helpers/tbbr/tbbr_tools.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -21,6 +21,7 @@
 # Build options added by this file:
 #
 #   KEY_ALG
+#   KEY_SIZE
 #   ROT_KEY
 #   TRUSTED_WORLD_KEY
 #   NON_TRUSTED_WORLD_KEY
@@ -52,6 +53,7 @@
 # packed in the FIP). Developers can use their own keys by specifying the proper
 # build option in the command line when building the Trusted Firmware
 $(if ${KEY_ALG},$(eval $(call CERT_ADD_CMD_OPT,${KEY_ALG},--key-alg)))
+$(if ${KEY_SIZE},$(eval $(call CERT_ADD_CMD_OPT,${KEY_SIZE},--key-size)))
 $(if ${HASH_ALG},$(eval $(call CERT_ADD_CMD_OPT,${HASH_ALG},--hash-alg)))
 $(if ${ROT_KEY},$(eval $(call CERT_ADD_CMD_OPT,${ROT_KEY},--rot-key)))
 $(if ${ROT_KEY},$(eval $(call CERT_ADD_CMD_OPT,${ROT_KEY},--rot-key,FWU_)))