primative boolean null?

I unable to explain why freemarker thinks this boolean primative is null. 
Any ideas? The method getCanDriveAccountNegative() returns boolean. I've 
tried isCanDriveAccountNegative(), too. Same result. I know that feeSetup 
is not null because the references before that all work.

                <tr><td>Account 
Subtype:</td><td>${feeSetup.accountSubType}</td></tr>
                <tr><td>Allow a fee to drive an account 
negative:</td><td>${feeSetup.canDriveAccountNegative?string}</td></tr>


09:26:56,272 line:271 ERROR [ContainerBase->invoke] Servlet.service() for 
servlet internaladmin threw exception
Expression feeSetup.canDriveAccountNegative is undefined on line 17, 
column 77 in global/views/feeConfirm.ftl.
The problematic instruction:
----------
==> ${feeSetup.canDriveAccountNegative?string} [on line 17, column 75 in 
global/views/feeConfirm.ftl]
 in include content [on line 68, column 17 in global/views/shell.ftl]
----------

Java backtrace for programmers:
----------
freemarker.core.InvalidReferenceException: Expression 
feeSetup.canDriveAccountNegative is undefined on line 17, column 77 in 
global/views/feeConfirm.ftl.
        at freemarker.core.TemplateObject.assertNonNull(
TemplateObject.java:124)
        at freemarker.core.TemplateObject.invalidTypeException(
TemplateObject.java:134)

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