diff --git a/source/ftl/map.c b/source/ftl/map.c
index 5c15857..9f7ca04 100644
--- a/source/ftl/map.c
+++ b/source/ftl/map.c
@@ -75,6 +75,9 @@ int read_page_group(struct ftl_map *map,
 	if (flash_read(map->dev, addr, group, sizeof *group) == 0)
 		return -1;
 
+	if (memcmp(group->magic, "FTL", 3) != 0)
+		return -1;
+
 	return 0;
 }