freemarker error: Expected hash, evaluated instead to ...

I've created a custom collection that implements iterator and returns 
another custom object - NotesDocWrapper (wraps a Lotus Domino Document 
object.) My template then lists the docs collection I placed in the root 
hash and iterates over the doc accessing a field like so:
<#list docs as doc>
<li>${doc.Subject}</li>
</#list>
The NotesDocWrapper implements TemplateModel and has a get method so it 
can return a Notes Document field using the standard template dot syntax 
as used above. I've used the NotesDocWrapper by itself, dropping it into 
the root hash successfully, but when I attempt to nest it in this manner 
I get a freemarker exception (see full stacktrace at bottom of post)

How do I prevent Freemarker from expecting a hash instead of using the 
wrapper I supplied for the nested object? (assuming this is the problem) 
Any tips are appreciated.

-----BEGIN STACKTRACE-----
Expected hash. doc evaluated instead to 
com.cmti.freemarker.NotesDocWrapper on line 9, column 7 in VETest1.ftl.
The problematic instruction:
----------
==> ${doc.Subject} [on line 9, column 5 in VETest1.ftl]
----------

Java backtrace for programmers:
----------
freemarker.template.TemplateException: Expected hash. doc evaluated 
instead to com.cmti.freemarker.NotesDocWrapper on line 9, column 7 in 
VETest1.ftl.
	at 
freemarker.core.TemplateObject.invalidTypeException(TemplateObject.java:135)
	at freemarker.core.Dot._getAsTemplateModel(Dot.java:78)
	at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
	at freemarker.core.Expression.getStringValue(Expression.java:93)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:76)
	at freemarker.core.Environment.visit(Environment.java:209)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:209)
	at freemarker.core.IteratorBlock$Context.runLoop(IteratorBlock.java:167)
	at freemarker.core.Environment.visit(Environment.java:416)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:102)
	at freemarker.core.Environment.visit(Environment.java:209)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:209)
	at freemarker.core.Environment.process(Environment.java:189)
	at freemarker.template.Template.process(Template.java:237)
	at FreemarkerTester.main(FreemarkerTester.java:54)


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