Inappropriate Error - Variable Arg Might Not Have Been Initialized

Consider the following simple code:
 
public class Test {
      private final int arg;
      private final Runnable runnable1 = new Runnable() {
            @Override
            public void run() {
                 // No errors here, exactly as expected
                 System.out.println("ARG: " + arg);

[Code] ....
 
The java compiler (version 1.8.0-b132) produces the following error when compiling this code:

"Error:(14, 46) java: variable arg might not have been initialized"
 
Actually, I do not expect the error here.

Both declarations 'runnable1' and 'runnable2' are essentially the same: these are just Runnable objects accessing value of the 'arg' field (which is initialized in the constructor).

The only difference between the declarations is that 'runnable1' - is an old-fashion instantiation of Runnable, whereas 'runnable2' - is an instantiation of Runnable via a lambda expression.