diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 27de243..306049e 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -644,7 +644,7 @@
 		unsigned long pud_phys;
 		pud_t *pud;
 
-		next = start + PGDIR_SIZE;
+		next = (start + PGDIR_SIZE) & PGDIR_MASK;
 		if (next > end)
 			next = end;