diff --git a/include/arch/aarch64/arch.h b/include/arch/aarch64/arch.h
index 13927bd..e9d22b6 100644
--- a/include/arch/aarch64/arch.h
+++ b/include/arch/aarch64/arch.h
@@ -962,6 +962,7 @@
 #define EC_AARCH64_HVC			U(0x16)
 #define EC_AARCH64_SMC			U(0x17)
 #define EC_AARCH64_SYS			U(0x18)
+#define EC_IMP_DEF_EL3			U(0x1f)
 #define EC_IABORT_LOWER_EL		U(0x20)
 #define EC_IABORT_CUR_EL		U(0x21)
 #define EC_PC_ALIGN			U(0x22)