code: public void setParameter(String name, String value) {
  		String escapedValue = RFC2396UrlDecoder.encode(value);
  		super.setParameter(name, value);
  		try {
  		    // https://code.google.com/p/sipservlets/issues/detail?id=170
  			telUrl.setParameter(name, "".equals(escapedValue) ? null : escapedValue);
  		} catch (ParseException e) {
  			throw new IllegalArgumentException("Problem setting parameter", e);
  		}
  	}
docs: /*
  (non-Javadoc)
  @see org.mobicents.servlet.sip.address.ParameterableImpl#setParameter(java.lang.String, java.lang.String)