Test using HttpURLConnection without restricted headers

As part of my JUnit test suite I have to test sending an HTTP request with one of HttpURLConnection restricted headers.

conn.setRequestProperty("Host", host);

In @BeforeTest I can allow the restricted headers, but that won't work when the class' static initializer is executed beforehand:

@BeforeClass
public static void init() {
    // this won't work because HttpURLConnection has already been initialized
    System.setProperty("sun.net.http.allowRestrictedHeaders", "true");
}

What would be another method of allowing the restricted headers that will work like allowRestrictedHeaders?