diff --git a/source/ftl/map.c b/source/ftl/map.c
index 6989a33..4463b1b 100644
--- a/source/ftl/map.c
+++ b/source/ftl/map.c
@@ -301,7 +301,7 @@ static int find_head(struct ftl_map *map)
 
 static void reset_map(struct ftl_map *map)
 {
-	map->log2_erase_size = dev->log2_block_size;
+	map->log2_erase_size = map->dev->log2_block_size;
 	map->log2_page_size = ilog2(1 * KIB);
 	map->log2_block_size = ilog2(64 * KIB);