diff --git a/fitsio2.h b/fitsio2.h
index 27793a7..66e4bcb 100644
--- a/fitsio2.h
+++ b/fitsio2.h
@@ -96,7 +96,7 @@ extern int Fitsio_Pthread_Status;
 #define BYTESWAPPED FALSE
 #define LONGSIZE 32
 
-#elif defined(__ia64__)  || defined(__x86_64__)
+#elif defined(__ia64__)  || defined(__x86_64__) || defined(__AARCH64EL__)
                   /*  Intel itanium 64-bit PC, or AMD opteron 64-bit PC */
 #define BYTESWAPPED TRUE
 #define LONGSIZE 64   
@@ -107,7 +107,7 @@ extern int Fitsio_Pthread_Status;
 #define MACHINE NATIVE
 #define LONGSIZE 64
 
-#elif defined(__powerpc64__) || defined(__64BIT__) /* IBM 64-bit AIX powerpc*/
+#elif defined(__powerpc64__) || defined(__64BIT__) || defined(__AARCH64EB__) /* IBM 64-bit AIX powerpc*/
                               /* could also test for __ppc64__ or __PPC64 */
 #define BYTESWAPPED FALSE
 #define MACHINE NATIVE