diff --git a/Utilities/KWIML/ABI.h.in b/Utilities/KWIML/ABI.h.in
index f93ddbaae..7f4772ae5 100644
--- a/Utilities/KWIML/ABI.h.in
+++ b/Utilities/KWIML/ABI.h.in
@@ -418,6 +418,14 @@ suppression macro @KWIML@_ABI_NO_VERIFY was defined.
 #elif defined(__vax__)
 # define @KWIML@_ABI_ENDIAN_ID @KWIML@_ABI_ENDIAN_ID_BIG
 
+/* Aarch64 */
+#elif defined(__aarch64__)
+# if !defined(__AARCH64EB__)
+#  define @KWIML@_ABI_ENDIAN_ID @KWIML@_ABI_ENDIAN_ID_LITTLE
+# else
+#  define @KWIML@_ABI_ENDIAN_ID @KWIML@_ABI_ENDIAN_ID_BIG
+# endif
+
 /* Unknown CPU */
 #elif !defined(@KWIML@_ABI_NO_ERROR_ENDIAN)
 # error "Byte order of target CPU unknown."