diff --git a/mm/page_ext.c b/mm/page_ext.c
index 2a52fd9ed464aa7d780dc50440b7f09989ad15ce..6242afb24d8479118019c084211280c160e301f1 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -201,7 +201,7 @@ void __init page_ext_init_flatmem(void)
 	panic("Out of memory");
 }
 
-#else /* CONFIG_FLATMEM */
+#else /* CONFIG_SPARSEMEM */
 
 struct page_ext *lookup_page_ext(const struct page *page)
 {