Issue binding multiple elements in collection after upgrading from 1.1.5 -> 1.2.1

NOTE: attached is a runnable sample: run "mvn test" to see it running successfully, then changed the jibx.version property in pom.xml and re-run to see it failing with a similar error to below.

We marshall the following type of XML where Option, Color and UsedFeature all extend a Feature class:

<features>
<option>
<feature ..
</option>
<option>
<feature ..
</option
<color>
<feature ..
</color>
<color>
<feature ..
</color>
<usedFeature>
<feature...
</usedFeature>
</features>

The following bindings XML is used to define a Set of Features belonging to another object. Any one of option, color or usedFeature can occur any number of times:

<mapping ns="http://www.edmunds.com/esbservices/schemas" class="com.edmunds.vehicle.coherence.ModelYearImpl"
name="modelYear" post-set="postset">
...
<structure name="features" field="features" usage="optional" map-as="features-set"/>
....
</mapping>

<mapping abstract="true" type-name="features-set" class="java.util.Set" create-type="java.util.HashSet">
<collection ordered="false">
<structure name="option" type="com.edmunds.vehicle.coherence.OptionImpl"
marshaller="com.edmunds.vehicle.util.jibx.FeatureIdRefMapper"
unmarshaller="com.edmunds.vehicle.util.jibx.FeatureIdRefMapper"/>
<structure name="color" type="com.edmunds.vehicle.coherence.ColorImpl"
marshaller="com.edmunds.vehicle.util.jibx.FeatureIdRefMapper"
unmarshaller="com.edmunds.vehicle.util.jibx.FeatureIdRefMapper"/>
<structure name="usedFeature" type="com.edmunds.vehicle.coherence.UsedFeatureImpl"
marshaller="com.edmunds.vehicle.util.jibx.FeatureIdRefMapper"
unmarshaller="com.edmunds.vehicle.util.jibx.FeatureIdRefMapper"/>
</collection>
</mapping>

This all worked fine with Jibx 1.1.5, but with 1.2.1 I get an error informing me that it was expecting all of the elements to be of the same type (option OR color OR usedFeature), i.e.

java.lang.RuntimeException: org.jibx.runtime.JiBXException: Expected "

features" end tag, found "

color" start tag (line 1, col 75244)
at com.edmunds.vehicle.end2end.VehicleEndToEndTest.saveMakeTree(VehicleEndToEndTest.java:135)
Caused by: org.jibx.runtime.JiBXException: Expected "

features" end tag, found "

color" start tag (line 1, col 75244)
at org.jibx.runtime.impl.UnmarshallingContext.parsePastCurrentEndTag(UnmarshallingContext.java:736)