diff -r 4fa24b4ac2f9 src/libmach/executable.c
--- a/src/libmach/executable.c	Tue Aug 20 08:21:58 2013 -0700
+++ b/src/libmach/executable.c	Tue Aug 20 20:41:24 2013 +0200
@@ -1076,7 +1076,7 @@
 			return 0;
 		}
 
-		if (mp->cpusubtype != MACH_CPU_SUBTYPE_X86) {
+		if (mp->cpusubtype != MACH_CPU_SUBTYPE_X86_64) {
 			werrstr("bad MACH cpu subtype - not amd64");
 			return 0;
 		}
diff -r 4fa24b4ac2f9 src/libmach/macho.h
--- a/src/libmach/macho.h	Tue Aug 20 08:21:58 2013 -0700
+++ b/src/libmach/macho.h	Tue Aug 20 20:41:24 2013 +0200
@@ -87,6 +87,7 @@
 	MACH_CPU_TYPE_X86_64 = (1<<24)|7,
 	MACH_CPU_TYPE_X86 = 7,
 	MACH_CPU_SUBTYPE_X86 = 3,
+	MACH_CPU_SUBTYPE_X86_64 = (1<<31)|3,
 	MACH_EXECUTABLE_TYPE = 2,
 	MACH_SEGMENT_32 = 1,	/* 32-bit mapped segment */
 	MACH_SEGMENT_64 = 0x19,	/* 64-bit mapped segment */