diff --git a/plugins/dbms/maxdb/enumeration.py b/plugins/dbms/maxdb/enumeration.py
index 8fd2f4680..1f2b38130 100644
--- a/plugins/dbms/maxdb/enumeration.py
+++ b/plugins/dbms/maxdb/enumeration.py
@@ -77,8 +77,8 @@ class Enumeration(GenericEnumeration):
         rootQuery = queries[Backend.getIdentifiedDbms()].tables
 
         for db in dbs:
-            if not isinstance(db, basestring):
-                db = db[0]
+            if isinstance(db, (tuple, list)):
+                db = db[0] if db else ""
 
             randStr = randomStr()
             query = rootQuery.inband.query % (("'%s'" % db) if db != "USER" else 'USER')
diff --git a/plugins/dbms/mssqlserver/enumeration.py b/plugins/dbms/mssqlserver/enumeration.py
index 6eb637f28..589d63536 100644
--- a/plugins/dbms/mssqlserver/enumeration.py
+++ b/plugins/dbms/mssqlserver/enumeration.py
@@ -88,8 +88,8 @@ class Enumeration(GenericEnumeration):
 
         if any(isTechniqueAvailable(_) for _ in (PAYLOAD.TECHNIQUE.UNION, PAYLOAD.TECHNIQUE.ERROR)) or conf.direct:
             for db in dbs:
-                if not isinstance(db, basestring):
-                    db = db[0]
+                if isinstance(db, (tuple, list)):
+                    db = db[0] if db else ""
 
                 if conf.excludeSysDbs and db in self.excludeDbsList:
                     infoMsg = "skipping system database '%s'" % db
diff --git a/plugins/dbms/sybase/enumeration.py b/plugins/dbms/sybase/enumeration.py
index a3a74a174..bb69935d0 100644
--- a/plugins/dbms/sybase/enumeration.py
+++ b/plugins/dbms/sybase/enumeration.py
@@ -138,8 +138,8 @@ class Enumeration(GenericEnumeration):
         rootQuery = queries[Backend.getIdentifiedDbms()].tables
 
         for db in dbs:
-            if not isinstance(db, basestring):
-                db = db[0]
+            if isinstance(db, (tuple, list)):
+                db = db[0] if db else ""
 
             for blind in blinds:
                 randStr = randomStr()
diff --git a/plugins/generic/enumeration.py b/plugins/generic/enumeration.py
index 547bdde06..ec0b8da03 100644
--- a/plugins/generic/enumeration.py
+++ b/plugins/generic/enumeration.py
@@ -897,8 +897,8 @@ class Enumeration:
                     value = map(lambda x: (dbs[0], x), value)
 
                 for db, table in filterPairValues(value):
-                    if not isinstance(db, basestring):
-                        db = db[0]
+                    if isinstance(db, (tuple, list)):
+                        db = db[0] if db else ""
 
                     db = safeSQLIdentificatorNaming(db)
                     table = safeSQLIdentificatorNaming(table, True)