diff --git a/wagtail/wagtailadmin/forms.py b/wagtail/wagtailadmin/forms.py
index 1af8c44ba..393354e57 100644
--- a/wagtail/wagtailadmin/forms.py
+++ b/wagtail/wagtailadmin/forms.py
@@ -178,6 +178,12 @@ class CopyForm(forms.Form):
             # The slug is no longer valid, hence remove it from cleaned_data
             del cleaned_data['new_slug']
 
+        # Don't allow recursive copies into self
+        if cleaned_data.get('copy_subpages') and (self.page == parent_page or parent_page.is_descendant_of(self.page)):
+            self._errors['new_parent_page'] = self.error_class(
+                [_("You cannot copy a page into itself when copying subpages")]
+            )
+
         return cleaned_data
 
 
diff --git a/wagtail/wagtailadmin/tests/test_pages_views.py b/wagtail/wagtailadmin/tests/test_pages_views.py
index 785814e97..83dc4871e 100644
--- a/wagtail/wagtailadmin/tests/test_pages_views.py
+++ b/wagtail/wagtailadmin/tests/test_pages_views.py
@@ -2199,9 +2199,7 @@ class TestPageCopy(TestCase, WagtailTestUtils):
         )
 
     def test_page_copy_post_and_subpages_to_same_tree_branch(self):
-        # This tests the existing slug checking on page copy when changing the parent page
-
-        # Attempt to copy the page and changed the parent page
+        # This tests that a page cannot be copied into itself when copying subpages
         post_data = {
             'new_title': "Hello world 2",
             'new_slug': 'hello-world',
@@ -2209,7 +2207,14 @@ class TestPageCopy(TestCase, WagtailTestUtils):
             'copy_subpages': True,
         }
         response = self.client.post(reverse('wagtailadmin_pages:copy', args=(self.test_page.id,)), post_data)
-        self.assertEqual(response.status_code, 403)
+
+        # Should not be redirected (as the save should fail)
+        self.assertEqual(response.status_code, 200)
+
+        # Check that a form error was raised
+        self.assertFormError(
+            response, 'form', 'new_parent_page', "You cannot copy a page into itself when copying subpages"
+        )
 
     def test_page_copy_post_existing_slug_to_another_parent_page(self):
         # This tests the existing slug checking on page copy when changing the parent page