diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index dadb7e7..f4e17a5 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -106,7 +106,7 @@
 			buddy_pfn = __find_buddy_pfn(pfn, order);
 			buddy = page + (buddy_pfn - pfn);
 
-			if (pfn_valid_within(page_to_pfn(buddy)) &&
+			if (pfn_valid_within(buddy_pfn) &&
 			    !is_migrate_isolate_page(buddy)) {
 				__isolate_free_page(page, order);
 				isolated_page = true;