JSP Custom Tags as attribute values for other custom tags

[Dave]

I can use a custom tag as an attribute value in a standard html element
such as:

<img src="<ct:mypath file='x.gif'/>" />

I'm finding that I can't use the same kind of idiom inside a custom
tag. For example:

<ct:myimage filepath="<ct:mypath file='x.gif'/>" />

(I just typed these examples from my head. please forgive mismatching
delimiters and what not)

What I'm finding is that in the second case the custom tag mypath is not
being evaluated. It's being passed as a literal string even though
<rtexprvalue> is true for that attribute.

Is this an understood limitation of custom tags? Or should I expect
this to work?

Thanks.