diff --git a/lib/smc/aarch64/asm_smc.S b/lib/smc/aarch64/asm_smc.S
index 2b305b9..48a80a3 100644
--- a/lib/smc/aarch64/asm_smc.S
+++ b/lib/smc/aarch64/asm_smc.S
@@ -12,14 +12,14 @@
 
 
 /* ---------------------------------------------------------------------------
- * smc_ret_values asm_tftf_smc64(uint64_t arg0,
- *					      uint64_t arg1,
- *					      uint64_t arg2,
- *					      uint64_t arg3,
- *					      uint64_t arg4,
- *					      uint64_t arg5,
- *					      uint64_t arg6,
- *					      uint64_t arg7);
+ * smc_ret_values asm_tftf_smc64(uint32_t arg0,
+ *				 u_register_t arg1,
+ *				 u_register_t arg2,
+ *				 u_register_t arg3,
+ *				 u_register_t arg4,
+ *				 u_register_t arg5,
+ *				 u_register_t arg6,
+ *				 u_register_t arg7);
  * ---------------------------------------------------------------------------
  */
 func asm_tftf_smc64
diff --git a/lib/smc/aarch64/smc.c b/lib/smc/aarch64/smc.c
index 06b841c..cbe4bb9 100644
--- a/lib/smc/aarch64/smc.c
+++ b/lib/smc/aarch64/smc.c
@@ -7,14 +7,14 @@
 #include <stdint.h>
 #include <tftf.h>
 
-smc_ret_values asm_tftf_smc64(u_register_t arg0,
-					u_register_t arg1,
-					u_register_t arg2,
-					u_register_t arg3,
-					u_register_t arg4,
-					u_register_t arg5,
-					u_register_t arg6,
-					u_register_t arg7);
+smc_ret_values asm_tftf_smc64(uint32_t arg0,
+			      u_register_t arg1,
+			      u_register_t arg2,
+			      u_register_t arg3,
+			      u_register_t arg4,
+			      u_register_t arg5,
+			      u_register_t arg6,
+			      u_register_t arg7);
 
 smc_ret_values tftf_smc(const smc_args *args)
 {