SSIS XML datasource - unbounded elements are NULL

We're experiencing a problem while trying to import an XML file using SSIS. We have a more complex XML + XSD for which this problem occurs, but we were able to reproduce it on its own.

We have an XML file with several elements. We generated the XSD from it. Using the data visualizer we see that 4 rows are found, but the values are NULL.

What are we overlooking, or how can we solve this?

XML

<root>
  <index>a</index>
  <index>b</index>
  <index>n</index>
  <index>x</index>
</root>

XSD

<?xml version="1.0" encoding="Windows-1252"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://ift.tt/tphNwY">
  <xs:element name="root">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" name="index" type="xs:string" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

Screenshot

Yes, I've seen this one: SSIS XMLSource only seeing null values in XML variable - but changing the source XML is not really an option for us.