javac fails to produce an error on @Override annotations for 1.5 source

FULL PRODUCT VERSION :
java version "1.6.0_20"
Java(TM) SE Runtime Environment (build 1.6.0_20-b02)
Java HotSpot(TM) 64-Bit Server VM (build 16.3-b01, mixed mode)

javac 1.6.0_20


ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7600]

A DESCRIPTION OF THE PROBLEM :
Java 6 allows @Override annotations on initial implementations of methods from interfaces, as well as declaration of super functions in derived interfaces, while Java 5 will generate a compiler error. However, when specifying the source level as 1.5 on the compiler command line, Java 6 does NOT produce an error.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
create Test.java file that defines an interface and another interface which extends it, declares the same method and specifies the @Override annotation on the derived interface.

execute command 'javac -source 1.5 Test.java'



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
the same error you would get from a java 5 compiler:

Test.java:7: method does not override a method from its superclass
                                                        @Override public void foo();
ACTUAL -
no output on stdout or stderr. Class compiled successfully.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class Test {
  public interface A { public void foo(); }
  public interface B extends A { @Override public void foo(); }
}

---------- END SOURCE ----------