diff --git a/ostap/io/compress_shelve.py b/ostap/io/compress_shelve.py
index 2df3316c..dbec81f5 100755
--- a/ostap/io/compress_shelve.py
+++ b/ostap/io/compress_shelve.py
@@ -246,7 +246,7 @@ def __init__(
         self.__opened = False        
         dbase = dbopen ( self.dbname , flag = mode , dbtype = dbtype , **kwargs )
         self.__opened        = True
-        if dbase and 'r' != mode and hasattr ( dbase , 'sync' ) : dbase.sync()
+        if 'r' != mode and hasattr ( dbase , 'sync' ) : dbase.sync()
         
         # =======================================================================
         ## all files after dbopen 
@@ -269,6 +269,7 @@ def __init__(
         # ======================================================================
         ## actual type of underlying database 
         self.__dbtype        =  whichdb ( self.dbname ) ## actual dbtype 
+        if not self.dbtype : logger.error  ( 'Type of DB is no determined!' )
         
         # ======================================================================
         ## expected files for the given DB type 
diff --git a/ostap/io/tests/test_io_shelves.py b/ostap/io/tests/test_io_shelves.py
index c27085a0..73e23a07 100755
--- a/ostap/io/tests/test_io_shelves.py
+++ b/ostap/io/tests/test_io_shelves.py
@@ -172,6 +172,11 @@ def test_shelves1():
         'sqlite'    ,
         'sqlite3'   ,
         'dbm.gnu'   ,
+        'dbm.ndbm'  ,
+        'dbm.dumb'  ,
+        'dbhash'    ,
+        'dbm'       ,        
+        'gdbm'      ,        
         'dumbdbm'   ,
         'std'       ,
     ]