diff --git a/sysdefs.h b/sysdefs.h
index d145cd5..31b08b1 100644
--- a/sysdefs.h
+++ b/sysdefs.h
@@ -526,6 +526,32 @@ typedef unsigned long Card64;
 
 #endif /* __alpha */
 
+
+#ifdef __x86_64
+#define ARCHPRNAME "x86_64"
+
+#ifdef __linux__
+#define ARCHSYSNAME "unknown-linux"
+#define DEFSMADE
+#define OPENRDMODE "r"
+#define OPENWRMODE "w"
+#define OPENUPMODE "r+"
+#define IEEEFLOAT
+typedef signed char Integ8;
+typedef unsigned char Card8;
+typedef signed short Integ16;
+typedef unsigned short Card16;
+#define HAS16
+typedef signed int Integ32;
+typedef unsigned int Card32;
+typedef signed long Integ64;
+typedef unsigned long Card64;
+#define HAS64
+#define LOCALE_NLS
+#endif
+
+#endif /* __x86_64 */
+
 /*===========================================================================*/
 /* Intel i386 platforms */