diff --git a/core/includes/form.inc b/core/includes/form.inc
index 9e48ba5b09..3383ead668 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -485,7 +485,12 @@ function template_preprocess_form_element(&$variables) {
   $variables['label'] = ['#theme' => 'form_element_label'];
   $variables['label'] += array_intersect_key($element, array_flip(['#id', '#required', '#title', '#title_display']));
   $variables['label']['#attributes'] = $element['#label_attributes'];
-  $variables['label']['#for'] = $element['#label_for'];
+  if (!empty($element['#label_for'])) {
+    $variables['label']['#for'] = $element['#label_for'];
+    if (!empty($element['#id'])) {
+      $variables['label']['#id'] = $element['#id'] . '--label';
+    }
+  }
 
   $variables['children'] = $element['#children'];
 }
diff --git a/core/modules/file/src/Tests/FileFieldDisplayTest.php b/core/modules/file/src/Tests/FileFieldDisplayTest.php
index 1b7e534211..96556e29d0 100644
--- a/core/modules/file/src/Tests/FileFieldDisplayTest.php
+++ b/core/modules/file/src/Tests/FileFieldDisplayTest.php
@@ -105,6 +105,9 @@ public function testNodeDisplay() {
     $this->clickLink(t('Back to content editing'));
     $this->assertRaw($field_name . '[0][display]', 'First file appears as expected.');
     $this->assertRaw($field_name . '[1][display]', 'Second file appears as expected.');
+
+    // Regression test. Verify the file fields don't contain duplicate HTML IDs.
+    $this->assertNoDuplicateIds();
   }
 
   /**