diff --git a/apps/emqx_durable_storage/src/emqx_ds_storage_layer.erl b/apps/emqx_durable_storage/src/emqx_ds_storage_layer.erl
index 32ca85935..4140c0ed7 100644
--- a/apps/emqx_durable_storage/src/emqx_ds_storage_layer.erl
+++ b/apps/emqx_durable_storage/src/emqx_ds_storage_layer.erl
@@ -368,7 +368,7 @@ rocksdb_open(Shard, Options) ->
 
 -spec db_dir(shard_id()) -> file:filename().
 db_dir({DB, ShardId}) ->
-    filename:join("data", lists:flatten([atom_to_list(DB), $:, atom_to_list(ShardId)])).
+    filename:join(["data", atom_to_list(DB), atom_to_list(ShardId)]).
 
 %%--------------------------------------------------------------------------------
 %% Schema access