diff --git a/csst_common/data_manager.py b/csst_common/data_manager.py
index 0d50b80609ce9ddb7092a53e8c488e11792158bc..34ec45ecafb29257ca448a395c40c142c16e953d 100644
--- a/csst_common/data_manager.py
+++ b/csst_common/data_manager.py
@@ -517,12 +517,21 @@ class CsstMsDataManager:
 
         """
         assert detector in self.available_detectors
-        if self.ver_sim in ["C5.2", "C6.1"]:
-            fn = f"{self.telescope}_{self.instrument}_{self.project}_{self.obs_type}_{self.exp_start}_{self.exp_stop}_" \
-                 f"{self.obs_id}_{detector:02d}_{post}"
+        if post == ".fits":
+            # no additional suffix
+            if self.ver_sim in ["C5.2", "C6.1"]:
+                fn = f"{self.telescope}_{self.instrument}_{self.project}_{self.obs_type}_{self.exp_start}_{self.exp_stop}_" \
+                     f"{self.obs_id}_{detector:02d}{post}"
+            else:
+                fn = f"{self.telescope}_{self.instrument}_{self.project}_{self.obs_type}_{self.exp_start}_{self.exp_stop}_" \
+                     f"{self.obs_id}_{detector:02d}_L1_V{self.version}{post}"
         else:
-            fn = f"{self.telescope}_{self.instrument}_{self.project}_{self.obs_type}_{self.exp_start}_{self.exp_stop}_" \
-                 f"{self.obs_id}_{detector:02d}_L1_V{self.version}_{post}"
+            if self.ver_sim in ["C5.2", "C6.1"]:
+                fn = f"{self.telescope}_{self.instrument}_{self.project}_{self.obs_type}_{self.exp_start}_{self.exp_stop}_" \
+                     f"{self.obs_id}_{detector:02d}_{post}"
+            else:
+                fn = f"{self.telescope}_{self.instrument}_{self.project}_{self.obs_type}_{self.exp_start}_{self.exp_stop}_" \
+                     f"{self.obs_id}_{detector:02d}_L1_V{self.version}_{post}"
         return os.path.join(self.dir_l1, fn)
 
     def get_bias(self, detector=6):