diff --git a/tweetbutton.module b/tweetbutton.module
--- a/tweetbutton.module
+++ b/tweetbutton.module
@@ -80,7 +80,7 @@ function tweetbutton_permission() {
  * Implementation of hook_node_view()
  */
 function tweetbutton_node_view($node, $view_mode) {
-  if (in_array($node->type, variable_get('tweetbutton_node_types', array('article'))) 
+  if (in_array($node->type, variable_get('tweetbutton_node_types', array('article')), TRUE) 
     && in_array($view_mode, variable_get('tweetbutton_node_location', array('full')))
     && user_access('access tweetbutton')) {