diff --git a/app/models/Data/Base.php b/app/models/Data/Base.php
index 59a92be..ed81300 100644
--- a/app/models/Data/Base.php
+++ b/app/models/Data/Base.php
@@ -18,7 +18,7 @@ class Base extends Model
      * @param boolean $allFields
      * @return bool
      */
-    public function hasChanged($fieldName = null, $allFields = false)
+    public function hasChanged($fieldName = null, bool $allFields = false) : bool
     {
         return $this->hasSnapshotData() === false
             || parent::hasChanged($fieldName, $allFields);