Groovy Mixins Can't Satisfy Abstract Class Requirements

Using the mixin annotation I can add mixins to classes, however those mixins cannot fulfill abstract class requirements. For example, the following code throws compilation exceptions:

class M

abstract class A

@Mixin(M)
class B extends A {
}

def b = new B()
print "$

\n"
print "$

\n"

When attempting to run this code I get:

/private/tmp/runner.groovy: 10: Can't have an abstract method in a non-abstract class. The class 'B' must be declared abstract or the method 'java.lang.Object getFoo()' must be implemented.
@ line 10, column 1.
@Mixin(M)
^

/private/tmp/runner.groovy: 10: Can't have an abstract method in a non-abstract class. The class 'B' must be declared abstract or the method 'void setFoo(java.lang.Object)' must be implemented.
@ line 10, column 1.
@Mixin(M)
^

2 errors