immutables: Cannot find symbol: class Immutable

I have Immutables working fine in Eclipse with m2e-apt. But when I try to build the same project with mvn clean compile, I get compile errors that start with “cannot find symbol: class Immutable” and continue with many more “cannot find symbol” errors because the class that should have been generated, let’s call it Foo, by that @Immutable wasn’t. The strange thing is that this @Immutable AbstractFoo class is just one of many nested @Immutable classes and the other classes are being generated fine. So the error, “cannot find symbol: class Immutable”, only for the declaration on AbstractFoo doesn’t make sense because the @Immutable declaration is the same as all of the others in the same file that are working.

I tried to reproduce the problem in a simpler test project, but I wasn’t able to. So I copied the main project src to the test project src and then the same compile errors appeared. I started deleting other classes that reference the should-be-generated Foo and once they (and references to them) were deleted, the test project then compiled successfully. So it appears that the issue is related to other classes referencing the class that will be generated by an @Immutable.

Does this make sense? Is this a bug that can be fixed or do I need to use a workaround? Am I wrong to reference generated classes or to create nested @Immutable classes without using @Enclosing?