collection null although initialized

[Michael Simons]

Hello,

Given two classes like:
class A {
  Set<B> members = new HashSet<B>(13); // We initialize the set
  ...
  Map<String,String> getMembersMap() {
    Map<String,String> m = new HashMap<String, String>(members.size()); // We 
get a NPE here!
    ...
    return m;
  }
}
class B {...}

Is this a known issue?
Do we have to always check for a null collection even if we initialized it?

kind regards,
Michael