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