Index: src/applications/maniphest/controller/ManiphestBatchEditController.php
===================================================================
--- src/applications/maniphest/controller/ManiphestBatchEditController.php
+++ src/applications/maniphest/controller/ManiphestBatchEditController.php
@@ -55,8 +55,7 @@
         ->setURI('/maniphest/?ids='.$task_ids);
     }
 
-    $handle_phids = mpull($tasks, 'getOwnerPHID');
-    $handles = $this->loadViewerHandles($handle_phids);
+    $handles = ManiphestTaskListView::loadTaskHandles($user, $tasks);
 
     $list = new ManiphestTaskListView();
     $list->setTasks($tasks);
Index: src/applications/maniphest/controller/ManiphestTaskListController.php
===================================================================
--- src/applications/maniphest/controller/ManiphestTaskListController.php
+++ src/applications/maniphest/controller/ManiphestTaskListController.php
@@ -40,7 +40,7 @@
     $group_parameter = nonempty($query->getParameter('group'), 'priority');
     $order_parameter = nonempty($query->getParameter('order'), 'priority');
 
-    $handles = $this->loadTaskHandles($tasks);
+    $handles = ManiphestTaskListView::loadTaskHandles($viewer, $tasks);
     $groups = $this->groupTasks(
       $tasks,
       $group_parameter,
@@ -114,30 +114,6 @@
       ));
   }
 
-  private function loadTaskHandles(array $tasks) {
-    assert_instances_of($tasks, 'ManiphestTask');
-
-    $phids = array();
-    foreach ($tasks as $task) {
-      $assigned_phid = $task->getOwnerPHID();
-      if ($assigned_phid) {
-        $phids[] = $assigned_phid;
-      }
-      foreach ($task->getProjectPHIDs() as $project_phid) {
-        $phids[] = $project_phid;
-      }
-    }
-
-    if (!$phids) {
-      return array();
-    }
-
-    return id(new PhabricatorHandleQuery())
-      ->setViewer($this->getRequest()->getUser())
-      ->withPHIDs($phids)
-      ->execute();
-  }
-
   private function groupTasks(array $tasks, $group, array $handles) {
     assert_instances_of($tasks, 'ManiphestTask');
     assert_instances_of($handles, 'PhabricatorObjectHandle');
Index: src/applications/maniphest/view/ManiphestTaskListView.php
===================================================================
--- src/applications/maniphest/view/ManiphestTaskListView.php
+++ src/applications/maniphest/view/ManiphestTaskListView.php
@@ -53,11 +53,8 @@
       $item->setHref('/T'.$task->getID());
 
       if ($task->getOwnerPHID()) {
-        $owner = idx($handles, $task->getOwnerPHID());
-        // TODO: This should be guaranteed, see T3817.
-        if ($owner) {
-          $item->addByline(pht('Assigned: %s', $owner->renderLink()));
-        }
+        $owner = $handles[$task->getOwnerPHID()];
+        $item->addByline(pht('Assigned: %s', $owner->renderLink()));
       }
 
       $status = $task->getStatus();
@@ -109,4 +106,30 @@
     return $list;
   }
 
+  public static function loadTaskHandles(
+    PhabricatorUser $viewer,
+    array $tasks) {
+    assert_instances_of($tasks, 'ManiphestTask');
+
+    $phids = array();
+    foreach ($tasks as $task) {
+      $assigned_phid = $task->getOwnerPHID();
+      if ($assigned_phid) {
+        $phids[] = $assigned_phid;
+      }
+      foreach ($task->getProjectPHIDs() as $project_phid) {
+        $phids[] = $project_phid;
+      }
+    }
+
+    if (!$phids) {
+      return array();
+    }
+
+    return id(new PhabricatorHandleQuery())
+      ->setViewer($viewer)
+      ->withPHIDs($phids)
+      ->execute();
+  }
+
 }