diff --git a/mm/page_ext.c b/mm/page_ext.c
index 2a52fd9ed464..6242afb24d84 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -201,7 +201,7 @@ fail:
 	panic("Out of memory");
 }
 
-#else /* CONFIG_FLATMEM */
+#else /* CONFIG_SPARSEMEM */
 
 struct page_ext *lookup_page_ext(const struct page *page)
 {