RowCsvInputFormat bug on parsing tsv

char fieldDelim = '\t';
    TypeInformation<?>[] fieldTypes = new TypeInformation<?>[51];
    for (int i = 0; i < fieldTypes.length; i++) {
      fieldTypes[i] = BasicTypeInfo.STRING_TYPE_INFO;
    }
    int[] fieldMask = new int[fieldTypes.length];
    for (int i = 0; i < fieldMask.length; i++) {
      fieldMask[i] = i;
    }
    RowCsvInputFormat csvIF = new RowCsvInputFormat(new Path(testCsv), fieldTypes, "\n", fieldDelim +"", 
       fieldMask, true);
    csvIF.setNestedFileEnumeration(true);
    DataSet<Row> csv = env.createInput(csvIF);
   csv.print()