diff --git a/bl1/bl1_fwu.c b/bl1/bl1_fwu.c
index 48f08d2..42a3ded 100644
--- a/bl1/bl1_fwu.c
+++ b/bl1/bl1_fwu.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -55,11 +55,11 @@
 /*******************************************************************************
  * Top level handler for servicing FWU SMCs.
  ******************************************************************************/
-register_t bl1_fwu_smc_handler(unsigned int smc_fid,
-			register_t x1,
-			register_t x2,
-			register_t x3,
-			register_t x4,
+u_register_t bl1_fwu_smc_handler(unsigned int smc_fid,
+			u_register_t x1,
+			u_register_t x2,
+			u_register_t x3,
+			u_register_t x4,
 			void *cookie,
 			void *handle,
 			unsigned int flags)
@@ -76,7 +76,7 @@
 		SMC_RET1(handle, bl1_fwu_image_execute(x1, &handle, flags));
 
 	case FWU_SMC_IMAGE_RESUME:
-		SMC_RET1(handle, bl1_fwu_image_resume(x1, &handle, flags));
+		SMC_RET1(handle, bl1_fwu_image_resume((register_t)x1, &handle, flags));
 
 	case FWU_SMC_SEC_IMAGE_DONE:
 		SMC_RET1(handle, bl1_fwu_sec_image_done(&handle, flags));
diff --git a/bl1/bl1_main.c b/bl1/bl1_main.c
index bff8d22..e11ead6 100644
--- a/bl1/bl1_main.c
+++ b/bl1/bl1_main.c
@@ -226,11 +226,11 @@
 /*******************************************************************************
  * Top level handler for servicing BL1 SMCs.
  ******************************************************************************/
-register_t bl1_smc_handler(unsigned int smc_fid,
-	register_t x1,
-	register_t x2,
-	register_t x3,
-	register_t x4,
+u_register_t bl1_smc_handler(unsigned int smc_fid,
+	u_register_t x1,
+	u_register_t x2,
+	u_register_t x3,
+	u_register_t x4,
 	void *cookie,
 	void *handle,
 	unsigned int flags)
@@ -269,12 +269,12 @@
  * BL1 SMC wrapper.  This function is only used in AArch32 mode to ensure ABI
  * compliance when invoking bl1_smc_handler.
  ******************************************************************************/
-register_t bl1_smc_wrapper(uint32_t smc_fid,
+u_register_t bl1_smc_wrapper(uint32_t smc_fid,
 	void *cookie,
 	void *handle,
 	unsigned int flags)
 {
-	register_t x1, x2, x3, x4;
+	u_register_t x1, x2, x3, x4;
 
 	assert(handle != NULL);
 
diff --git a/bl1/bl1_private.h b/bl1/bl1_private.h
index 927c7b8..2cfeeea 100644
--- a/bl1/bl1_private.h
+++ b/bl1/bl1_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -19,11 +19,11 @@
 
 void bl1_prepare_next_image(unsigned int image_id);
 
-register_t bl1_fwu_smc_handler(unsigned int smc_fid,
-		register_t x1,
-		register_t x2,
-		register_t x3,
-		register_t x4,
+u_register_t bl1_fwu_smc_handler(unsigned int smc_fid,
+		u_register_t x1,
+		u_register_t x2,
+		u_register_t x3,
+		u_register_t x4,
 		void *cookie,
 		void *handle,
 		unsigned int flags);