Unable to send SMS message in Android from variable

When I use this code:

String numberToSendFor = "21987654321";
SmsManager sms = SmsManager.getDefault();
sms.sendTextMessage(numberToSendFor, null, "Test Message", null, null);

The SMS Message is sent normally (and goes to sent messages list in my phone).

But, when I use this:

String numberToSendFor = "21987654321";
String messageToSend = "Test Message"; // put the message in a variable
SmsManager sms = SmsManager.getDefault();
sms.sendTextMessage(numberToSendFor, null, messageToSend, null, null);

The message don't is sent and don't goes to sent messages list.

What should I do to send message from a variable?

Thanks.