diff --git a/csst_dfs_api/common/utils.py b/csst_dfs_api/common/utils.py
index 8bf83b4ad5426606e1dcfb9da98fd318196e4e93..2e6204949ece79231604f9630fd8563dcfc0e019 100644
--- a/csst_dfs_api/common/utils.py
+++ b/csst_dfs_api/common/utils.py
@@ -92,13 +92,13 @@ def tuple_fields_dtypes(rec: tuple):
         if type(f) == int:
             dtypes.append('i8')
         elif type(f) == float:
-            dtypes.append('f8')        
+            dtypes.append('f8')
         elif type(f) == str:
-            dtypes.append('S2')
+            dtypes.append('V')
         elif type(f) == list:
-            dtypes.append('(12,)f8')       
+            dtypes.append('(12,)f8')
         else:
-            dtypes.append('S2')                
+            dtypes.append('V')
     dtypes = tuple(dtypes)
     return dtypes
 
diff --git a/csst_dfs_api/facility/level0.py b/csst_dfs_api/facility/level0.py
index 024804198590284c36ee6033873ab6f4c11134ac..f4a25de2cc5fd31305eca90012a8eef59278ef67 100644
--- a/csst_dfs_api/facility/level0.py
+++ b/csst_dfs_api/facility/level0.py
@@ -82,7 +82,7 @@ class Level0DataApi(object):
 
     def write(self, **kwargs):
         ''' insert a level0 data record into database
- 
+
         :param kwargs: Parameter dictionary, key items support:
             obs_id = [str],
             detector_no = [str],
diff --git a/tests/mbi/test_mbi_level2co.py b/tests/mbi/test_mbi_level2co.py
index 77d46c3bc9c29720e1b56ff3617faa43e0ec6ab2..fbcc79951f3c574e6ae55db394782275c191849d 100644
--- a/tests/mbi/test_mbi_level2co.py
+++ b/tests/mbi/test_mbi_level2co.py
@@ -1,6 +1,6 @@
 import unittest
 
-from csst_dfs_api.mbi.level2co import Level2CoApi
+from csst_dfs_api.mbi import Level2CoApi
 
 class MBILevel2CoDataTestCase(unittest.TestCase):