diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h
index 40227c9bf51b6a9da932d3efff8fddf40618c7ff..b0dece41dbc4628111f13db792bb271f1a3a9a98 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -870,7 +870,7 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk);
 /*
  * User space process size. 47bits minus one guard page.
  */
-#define TASK_SIZE64		(0x800000000000UL - 4096)
+#define TASK_SIZE64	((1UL << 47) - PAGE_SIZE)
 
 /* This decides where the kernel will search for a free chunk of vm
  * space during mmap's.