diff --git a/workflow/engine/src/BusinessModel/Cases.php b/workflow/engine/src/BusinessModel/Cases.php
index 84b662901..2c95c1d2c 100644
--- a/workflow/engine/src/BusinessModel/Cases.php
+++ b/workflow/engine/src/BusinessModel/Cases.php
@@ -495,6 +495,8 @@ class Cases
             $ws = new \wsBase();
             if ($variables) {
                 $variables = array_shift($variables);
+            } elseif ($variables == null) {
+                $variables = array(array());
             }
             $fields = $ws->newCaseImpersonate($processUid, $userUid, $variables, $taskUid);
             $array = json_decode(json_encode($fields), true);
diff --git a/workflow/engine/src/Services/Api/ProcessMaker/Cases.php b/workflow/engine/src/Services/Api/ProcessMaker/Cases.php
index 02df83ee6..14b5901f9 100644
--- a/workflow/engine/src/Services/Api/ProcessMaker/Cases.php
+++ b/workflow/engine/src/Services/Api/ProcessMaker/Cases.php
@@ -220,6 +220,7 @@ class Cases extends Api
      * @param string $usr_uid {@from body} {@min 32}{@max 32}
      * @param string $tas_uid {@from body} {@min 32}{@max 32}
      * @param array $variables {@from body}
+     *
      */
     public function doPostCaseImpersonate($pro_uid, $usr_uid, $tas_uid, $variables=null)
     {