diff --git a/mm/sparse.c b/mm/sparse.c
index 58cab48..62eef26 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -779,7 +779,13 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
 		goto out;
 	}
 
-	memset(memmap, 0, sizeof(struct page) * PAGES_PER_SECTION);
+#ifdef CONFIG_DEBUG_VM
+	/*
+	 * Poison uninitialized struct pages in order to catch invalid flags
+	 * combinations.
+	 */
+	memset(memmap, PAGE_POISON_PATTERN, sizeof(struct page) * PAGES_PER_SECTION);
+#endif
 
 	section_mark_present(ms);