diff --git a/plugins/dbms/mssqlserver/enumeration.py b/plugins/dbms/mssqlserver/enumeration.py
index 5131f2b45..c3b9a0229 100644
--- a/plugins/dbms/mssqlserver/enumeration.py
+++ b/plugins/dbms/mssqlserver/enumeration.py
@@ -311,7 +311,7 @@ class Enumeration(GenericEnumeration):
             colQuery = "%s%s" % (colCond, colCondParam)
             colQuery = colQuery % unsafeSQLIdentificatorNaming(column)
 
-            for db in dbs.keys():
+            for db in filter(None, dbs.keys()):
                 db = safeSQLIdentificatorNaming(db)
 
                 if conf.excludeSysDbs and db in self.excludeDbsList: