diff --git a/src/SharethisManager.php b/src/SharethisManager.php
index d6d2d67..ccf6e95 100644
--- a/src/SharethisManager.php
+++ b/src/SharethisManager.php
@@ -202,7 +202,7 @@ class SharethisManager implements SharethisManagerInterface {
    * {@inheritdoc}
    */
   public function toBoolean($val) {
-    if (strtolower(trim($val)) === 'false') {
+    if (strtolower(trim("$val")) === 'false') {
       return FALSE;
     }
     else {