diff --git a/sys/amd64/include/gdb_machdep.h b/sys/amd64/include/gdb_machdep.h
index d007eef4052..d8c25b90fea 100644
--- a/sys/amd64/include/gdb_machdep.h
+++ b/sys/amd64/include/gdb_machdep.h
@@ -29,7 +29,7 @@
 #ifndef _MACHINE_GDB_MACHDEP_H_
 #define	_MACHINE_GDB_MACHDEP_H_
 
-#define	GDB_BUFSZ	500
+#define	GDB_BUFSZ	(GDB_NREGS * 16)
 #define	GDB_NREGS	56
 #define	GDB_REG_PC	16