diff --git a/date_api/date_api.module b/date_api/date_api.module
index d85a8a5..b13af4c 100644
--- a/date_api/date_api.module
+++ b/date_api/date_api.module
@@ -500,7 +500,7 @@ class DateObject extends DateTime {
    */
   public function limitGranularity($granularity) {
     foreach ($this->granularity as $key => $val) {
-      if ($val != 'timezone' && !in_array($val, $granularity)) {
+      if ($val != 'timezone' && !in_array($val, $granularity, TRUE)) {
         unset($this->granularity[$key]);
       }
     }