Synchronized and local copies of variables

I'm looking at some legacy code which has the following idiom:

Map<String, Boolean> myMap = someGlobalInstance.getMap();
synchronized (myMap) {
    item = myMap.get(myKey);
}

The warning I get from Intelli-J's code inspections is:

Synchronization on local variable 'myMap'

Is this the appropriate synchronization and why?

Map<String, Boolean> myMap = someGlobalInstance.getMap();
synchronized (someGlobalInstance.getMap()) {
    item = myMap.get(myKey);
}