FileNotFound when read generated file

[XDean]

I create a file in processor. And it does exists in the Compilation.generatedFiles

mem:///CLASS_OUTPUT/META-INF/xdean/annotation/MethodRef

But when I try to read the content, FileNotFoundException happened.

java.io.FileNotFoundException
	at com.google.testing.compile.InMemoryJavaFileManager$InMemoryJavaFileObject.getCharContent(InMemoryJavaFileManager.java:181)
	...

I'm using compile-testing:0.13.