diff --git a/workflow/engine/classes/class.derivation.php b/workflow/engine/classes/class.derivation.php
index 05f1f3334..e2b5f5d3d 100755
--- a/workflow/engine/classes/class.derivation.php
+++ b/workflow/engine/classes/class.derivation.php
@@ -328,9 +328,10 @@ class Derivation
     /* get all users, from any task, if the task have Groups, the function expand the group
      *
      * @param   string  $sTasUid  the task uidUser
+     * @param   bool    $flagIncludeAdHocUsers
      * @return  Array   $users an array with userID order by USR_UID
      */
-    function getAllUsersFromAnyTask ($sTasUid)
+    function getAllUsersFromAnyTask($sTasUid, $flagIncludeAdHocUsers = false)
     {
         $users = array ();
         $c = new Criteria( 'workflow' );
@@ -338,7 +339,16 @@ class Derivation
         $c->addSelectColumn( TaskUserPeer::USR_UID );
         $c->addSelectColumn( TaskUserPeer::TU_RELATION );
         $c->add( TaskUserPeer::TAS_UID, $sTasUid );
-        $c->add( TaskUserPeer::TU_TYPE, 1 );
+
+        if ($flagIncludeAdHocUsers) {
+            $c->add(
+                $c->getNewCriterion(TaskUserPeer::TU_TYPE, 1, Criteria::EQUAL)->addOr(
+                $c->getNewCriterion(TaskUserPeer::TU_TYPE, 2, Criteria::EQUAL))
+            );
+        } else {
+            $c->add(TaskUserPeer::TU_TYPE, 1);
+        }
+
         $rs = TaskUserPeer::DoSelectRs( $c );
         $rs->setFetchmode( ResultSet::FETCHMODE_ASSOC );
         $rs->next();
@@ -1245,4 +1255,3 @@ class Derivation
         }
     }
 }
-
diff --git a/workflow/engine/classes/class.wsBase.php b/workflow/engine/classes/class.wsBase.php
index 97c7d14d3..4c082d685 100755
--- a/workflow/engine/classes/class.wsBase.php
+++ b/workflow/engine/classes/class.wsBase.php
@@ -2891,7 +2891,7 @@ class wsBase
 
             $tasUid = $aRow['TAS_UID'];
             $derivation = new Derivation();
-            $userList = $derivation->getAllUsersFromAnyTask( $tasUid );
+            $userList = $derivation->getAllUsersFromAnyTask($tasUid, true);
 
             if (! in_array( $userIdTarget, $userList )) {
                 $result = new wsResponse( 34, G::loadTranslation( 'ID_TARGET_USER_DOES_NOT_HAVE_RIGHTS' ) );
@@ -3370,4 +3370,3 @@ class wsBase
         }
     }
 }
-