diff --git a/csst_common/data_manager.py b/csst_common/data_manager.py
index 20af96e12748a935ba0e9f624978d26bf27638e7..09393613f2e68d1054e21a4a3e432844918f4fbd 100644
--- a/csst_common/data_manager.py
+++ b/csst_common/data_manager.py
@@ -1067,7 +1067,7 @@ class CsstMsFile(dict):
             print(rec)
             raise ae
         header = rec["data"].header
-        header["filter"] = rec["data"]["filter"]
+        header["filter"] = rec["data"].filter
         return CsstMsFile(
             filepath=os.path.join(dfs_root, rec["data"].file_path),
             ver_sim=ver_sim,