diff --git a/kernel/vm.c b/kernel/vm.c
index 4f65d4e..636f11a 100644
--- a/kernel/vm.c
+++ b/kernel/vm.c
@@ -65,9 +65,9 @@ kvminithart()
 // A 64-bit virtual address is split into five fields:
 //   39..63 -- must be zero.
 //   30..38 -- 9 bits of level-2 index.
-//   21..39 -- 9 bits of level-1 index.
+//   21..29 -- 9 bits of level-1 index.
 //   12..20 -- 9 bits of level-0 index.
-//    0..12 -- 12 bits of byte offset within the page.
+//    0..11 -- 12 bits of byte offset within the page.
 pte_t *
 walk(pagetable_t pagetable, uint64 va, int alloc)
 {