diff --git a/src/Form/DataTransformer/ModelToIdPropertyTransformer.php b/src/Form/DataTransformer/ModelToIdPropertyTransformer.php
index 0c41095e71b..1f7b2acddfc 100644
--- a/src/Form/DataTransformer/ModelToIdPropertyTransformer.php
+++ b/src/Form/DataTransformer/ModelToIdPropertyTransformer.php
@@ -97,7 +97,7 @@ public function reverseTransform($value)
                 continue;
             }
 
-            $collection[] = $this->modelManager->find($this->className, $id);
+            $collection->add($this->modelManager->find($this->className, $id));
         }
 
         return $collection;
diff --git a/src/Form/DataTransformer/ModelsToArrayTransformer.php b/src/Form/DataTransformer/ModelsToArrayTransformer.php
index 2768a02f4e1..6390e18fd38 100644
--- a/src/Form/DataTransformer/ModelsToArrayTransformer.php
+++ b/src/Form/DataTransformer/ModelsToArrayTransformer.php
@@ -153,7 +153,7 @@ public function reverseTransform($keys)
         // optimize this into a SELECT WHERE IN query
         foreach ($keys as $key) {
             if ($model = $this->modelManager->find($this->class, $key)) {
-                $collection[] = $model;
+                $collection->add($model);
             } else {
                 $notFound[] = $key;
             }