diff --git a/src/applications/differential/storage/DifferentialDiff.php b/src/applications/differential/storage/DifferentialDiff.php
--- a/src/applications/differential/storage/DifferentialDiff.php
+++ b/src/applications/differential/storage/DifferentialDiff.php
@@ -737,9 +737,10 @@
         $prop->delete();
       }
 
-      $viewstates = id(new DifferentialViewStateQuery())
+      $viewstate_query = id(new DifferentialViewStateQuery())
         ->setViewer($viewer)
         ->withObjectPHIDs(array($this->getPHID()));
+      $viewstates = new PhabricatorQueryIterator($viewstate_query);
       foreach ($viewstates as $viewstate) {
         $viewstate->delete();
       }
diff --git a/src/applications/differential/storage/DifferentialRevision.php b/src/applications/differential/storage/DifferentialRevision.php
--- a/src/applications/differential/storage/DifferentialRevision.php
+++ b/src/applications/differential/storage/DifferentialRevision.php
@@ -1033,9 +1033,10 @@
         $dummy_path->getTableName(),
         $this->getID());
 
-      $viewstates = id(new DifferentialViewStateQuery())
+      $viewstate_query = id(new DifferentialViewStateQuery())
         ->setViewer($viewer)
         ->withObjectPHIDs(array($this->getPHID()));
+      $viewstates = new PhabricatorQueryIterator($viewstate_query);
       foreach ($viewstates as $viewstate) {
         $viewstate->delete();
       }