In-Memory File System and cfpdfform

I have been messing with this for a while with no progress. I am trying to populate a PDF form using cfpdfform and save it to memory using something like this:

<cfpdfform action="populate" source="blankForm.pdf" destination="ram:///filledForm.pdf" overwrite="yes">

But I keep getting:

The ram:///filledForm.pdf file specified in the cfpdfform tag either does not exist or is not accessible by this tag.

Does cfpdfform not have the ability to populate and write to memory or am I doing something wrong? I can successfully write to memory with cfpdf. I also realize I can populate to a variable and then write the result to a file using cfpdf. At this point, I'm mostly curious if this is intended behavior or not.