diff --git a/include/asm-x86_64/pgtable.h b/include/asm-x86_64/pgtable.h
index 8fbf4dd..715fd94 100644
--- a/include/asm-x86_64/pgtable.h
+++ b/include/asm-x86_64/pgtable.h
@@ -131,7 +131,7 @@
 #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 
-#define USER_PTRS_PER_PGD	(TASK_SIZE/PGDIR_SIZE)
+#define USER_PTRS_PER_PGD	((TASK_SIZE-1)/PGDIR_SIZE+1)
 #define FIRST_USER_ADDRESS	0
 
 #ifndef __ASSEMBLY__