Case-sensitive values in an Tabular Model with a Oracle Datasource

Hi,Lets use an Oracle Database as Datasource for my Project. I use a "Select distinct ColumnA from Table" to build up a LookupTable in my Tabular Model. But it returns Dublicates!! eg:

When I fire the query from Oracle SQL Developer I got 2 Records "1N" and "1n". In the Grid View in SSDT I see 2 times "1N". ??

Collation Case Sensitive. OK, but how to solve that?

KR