I'm attempting to compile my Flex project with an ANT build script.

One of my MXML components references an external XML data file, like this:

<mx:XML id="treeData" source="assets/data/help.xml" />

When I build the project using Flex Builder, it compiles fine. However, when I try to compile it using ANT, I get the following error:

Error: Problem finding external XML: assets/data/help.xml

How come ANT isn't finding the XML file? Apparently it knows the source path otherwise it would not have found the component to begin with. I added the source path to the target anyway, but it doesn't seem to have made any difference:

<source-path path-element="${SRC}" />

Any ideas?