Ant: Custom tasks which define properties

My Ant build uses some custom tasks that define properties named in an attribute when executing the task. For example:

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Defines a property called build.platform which contains the platform name (e.g. windows-ia32 or solaris-sparc).

However, any references to the build.platform property are marked in the IDEA editor as being undefined. Naturally, I can see why this is, IDEA doesn't know anything about my custom task. But is there some way this can be improved? I see a lot of red in my build.xml files but they work perfectly :(