diff --git a/ProcessMaker/Repositories/TokenRepository.php b/ProcessMaker/Repositories/TokenRepository.php
index 7e3e00179a..ac00c94301 100644
--- a/ProcessMaker/Repositories/TokenRepository.php
+++ b/ProcessMaker/Repositories/TokenRepository.php
@@ -135,6 +135,10 @@ public function persistActivityActivated(ActivityInterface $activity, TokenInter
                     $evaluatedUsers = is_array($evaluatedUsers) ? $evaluatedUsers : [$evaluatedUsers];
                     $evaluatedGroups = is_array($evaluatedGroups) ? $evaluatedGroups : [$evaluatedGroups];
 
+                    // convert to array of strings
+                    $evaluatedUsers = array_map('strval', $evaluatedUsers);
+                    $evaluatedGroups = array_map('strval', $evaluatedGroups);
+
                     $token->self_service_groups = ['users' => $evaluatedUsers, 'groups' => $evaluatedGroups];
                     break;
                 case 'rule_expression':