symfony
diff --git a/‎src/Symfony/Component/Form/Extension/Core/EventListener/ResizeFormListener.php
Lines changed: 8 additions & 2 deletions b/‎src/Symfony/Component/Form/Extension/Core/EventListener/ResizeFormListener.php
Lines changed: 8 additions & 2 deletions
diff --git a/‎src/Symfony/Component/Form/Tests/Extension/Core/EventListener/ResizeFormListenerTest.php
Lines changed: 14 additions & 1 deletion b/‎src/Symfony/Component/Form/Tests/Extension/Core/EventListener/ResizeFormListenerTest.php
Lines changed: 14 additions & 1 deletion
@@ -199,7 +199,13 @@ public function onSubmit(FormEvent $event): void
         }
 
         if ($this->keepAsList) {
-            $formReindex = [];
+            $formReindex = $dataKeys = [];
+            foreach ($data as $key => $value) {
+                $dataKeys[] = $key;
+            }
+            foreach ($dataKeys as $key) {
+                unset($data[$key]);
+            }
             foreach ($form as $name => $child) {
                 $formReindex[] = $child;
                 $form->remove($name);
@@ -208,8 +214,8 @@ public function onSubmit(FormEvent $event): void
                 $form->add($index, $this->type, array_replace([
                     'property_path' => '['.$index.']',
                 ], $this->options));
+                $data[] = $child->getData();
             }
-            $data = array_values($data);
         }
 
         $event->setData($data);
 
@@ -310,7 +310,7 @@ public function testOnSubmitDealsWithObjectBackedIteratorAggregate()
         $this->assertArrayNotHasKey(2, $event->getData());
     }
 
-    public function testOnSubmitDealsWithArrayBackedIteratorAggregate()
+    public function testOnSubmitDealsWithDoctrineCollection()
     {
         $this->builder->add($this->getBuilder('1'));
 
@@ -323,6 +323,19 @@ public function testOnSubmitDealsWithArrayBackedIteratorAggregate()
         $this->assertArrayNotHasKey(2, $event->getData());
     }
 
+    public function testKeepAsListWorksWithTraversableArrayAccess()
+    {
+        $this->builder->add($this->getBuilder('1'));
+
+        $data = new \ArrayIterator([0 => 'first', 1 => 'second', 2 => 'third']);
+        $event = new FormEvent($this->builder->getForm(), $data);
+        $listener = new ResizeFormListener(TextType::class, keepAsList: true);
+        $listener->onSubmit($event);
+
+        $this->assertArrayNotHasKey(1, $event->getData());
+        $this->assertArrayNotHasKey(2, $event->getData());
+    }
+
     public function testOnSubmitDeleteEmptyNotCompoundEntriesIfAllowDelete()
     {
         $this->builder->setData(['0' => 'first', '1' => 'second']);