--- src/chm_lib.c.orig
+++ src/chm_lib.c
@@ -164,7 +164,7 @@ typedef unsigned long long      UInt64;
 
 /* x86-64 */
 /* Note that these may be appropriate for other 64-bit machines. */
-#elif __x86_64__ || __ia64__
+#elif __x86_64__ || __ia64__ || __arm64__
 typedef unsigned char           UChar;
 typedef short                   Int16;
 typedef unsigned short          UInt16;