newProxyInstance returns null

I am trying to use Java Reflection to call a method which takes a callback as an argument. I instantiate all of the objects with Java Reflection. Also, I am using a Java Dynamic Proxy Class as the callback argument.

The weird thing is the java.lang.reflect.Proxy.newProxyInstance() method returns null.

Here is the interface I want to instantiate as an anonymous object as a Java Dynamic Proxy Class:

public interface MyListener {
    void onEvent(String eventName);
}

And here is how I instantiate the interface via newProxyInstance():

Object callbackObject = null;

try {
    Class callbackClass = Class.forName("com.example.MyListener");

    Class[] interfaceArray = new Class[]{callbackClass};

    InvocationHandler invocationHandler = new InvocationHandler() {

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (method.getName().equals("onMyEvent")) {
                Log.d(TAG, "InvocationHandler.invoke onMyEvent");
            }
            return null;
        }
    };

    callbackObject = java.lang.reflect.Proxy.newProxyInstance(
            this.getClass().getClassLoader(),
            interfaceArray,
            invocationHandler);
}
catch (Throwable t) {
    Log.e(TAG, "newProxyInstance got exception [" + t + "] caused by [" + t.getCause() + "]");
}

Log.d(TAG, "callbackObject=[" + callbackObject + "]");

if (null == callbackObject) {
    Log.e(TAG, "callbackObject is null according to null check");
}
else {
    Log.d(TAG, "callbackObject is NOT null according to null check");
}

The log messages seem to conflict about whether callbackObject is null:

callbackObject=[null]
callbackObject is NOT null according to null check

According to Why does newInstance() return null? it's not possible for newProxyInstance() to return null because it gets the value from newInstance().

So how can the result of newProxyInstance() be null and not null?