diff --git a/QvitterPlugin.php b/QvitterPlugin.php
index 4360045..d6e7323 100644
--- a/QvitterPlugin.php
+++ b/QvitterPlugin.php
@@ -224,8 +224,12 @@ class QvitterPlugin extends Plugin {
 									'qvitter'); 									                                					
 		}					
 		
-		// if qvitter is opt-out, disable the default register page
-		if(self::settings('enabledbydefault')) {
+		// if qvitter is opt-out, disable the default register page (if we don't have a valid invitation code)
+        $code = $_POST['code'];
+        if(!empty($code)) {
+			$valid_code = Invitation::getKV('code', $code);			
+			}
+		if(self::settings('enabledbydefault') && empty($valid_code)) {
 			$m->connect('main/register',
 						array('action' => 'qvitter')); 			
 			}