diff --git a/CRM/Activity/Form/Search.php b/CRM/Activity/Form/Search.php
index 7e177c5a7098..f59e18c13b8d 100644
--- a/CRM/Activity/Form/Search.php
+++ b/CRM/Activity/Form/Search.php
@@ -413,7 +413,7 @@ public function getFormValues() {
    *   reference to the array of default values
    */
   public function setDefaultValues() {
-    return array_merge($this->getEntityDefaults($this->getDefaultEntity()), $this->_formValues);
+    return array_merge($this->getEntityDefaults($this->getDefaultEntity()), (array) $this->_formValues);
   }
 
   /**