diff --git a/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php b/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php
index df5e039cb08..b2386b489d3 100644
--- a/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php
+++ b/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php
@@ -325,25 +325,30 @@ class FileWidget extends WidgetBase implements ContainerFactoryPluginInterface {
    * This validator is used only when cardinality not set to 1 or unlimited.
    */
   public static function validateMultipleCount($element, FormStateInterface $form_state, $form) {
-    $parents = $element['#parents'];
-    $values = NestedArray::getValue($form_state->getValues(), $parents);
+    $values = NestedArray::getValue($form_state->getValues(), $element['#parents']);
 
-    array_pop($parents);
-    $current = count(Element::children(NestedArray::getValue($form, $parents))) - 1;
+    $array_parents = $element['#array_parents'];
+    array_pop($array_parents);
+    $previously_uploaded_count = count(Element::children(NestedArray::getValue($form, $array_parents))) - 1;
 
     $field_storage_definitions = \Drupal::entityManager()->getFieldStorageDefinitions($element['#entity_type']);
     $field_storage = $field_storage_definitions[$element['#field_name']];
-    $uploaded = count($values['fids']);
-    $count = $uploaded + $current;
-    if ($count > $field_storage->getCardinality()) {
-      $keep = $uploaded - $count + $field_storage->getCardinality();
+    $newly_uploaded_count = count($values['fids']);
+    $total_uploaded_count = $newly_uploaded_count + $previously_uploaded_count;
+    if ($total_uploaded_count > $field_storage->getCardinality()) {
+      $keep = $newly_uploaded_count - $total_uploaded_count + $field_storage->getCardinality();
       $removed_files = array_slice($values['fids'], $keep);
       $removed_names = array();
       foreach ($removed_files as $fid) {
         $file = File::load($fid);
         $removed_names[] = $file->getFilename();
       }
-      $args = array('%field' => $field_storage->getName(), '@max' => $field_storage->getCardinality(), '@count' => $uploaded, '%list' => implode(', ', $removed_names));
+      $args = [
+        '%field' => $field_storage->getName(),
+        '@max' => $field_storage->getCardinality(),
+        '@count' => $total_uploaded_count,
+        '%list' => implode(', ', $removed_names),
+      ];
       $message = t('Field %field can only hold @max values but there were @count uploaded. The following files have been omitted as a result: %list.', $args);
       drupal_set_message($message, 'warning');
       $values['fids'] = array_slice($values['fids'], 0, $keep);
diff --git a/core/modules/file/src/Tests/FileFieldTestBase.php b/core/modules/file/src/Tests/FileFieldTestBase.php
index a725099c226..307eb4d1593 100644
--- a/core/modules/file/src/Tests/FileFieldTestBase.php
+++ b/core/modules/file/src/Tests/FileFieldTestBase.php
@@ -36,6 +36,8 @@ abstract class FileFieldTestBase extends WebTestBase {
 
   /**
    * Retrieves a sample file of the specified type.
+   *
+   * @return \Drupal\file\FileInterface
    */
   function getTestFile($type_name, $size = NULL) {
     // Get a file to upload.
diff --git a/core/modules/file/src/Tests/FileFieldWidgetTest.php b/core/modules/file/src/Tests/FileFieldWidgetTest.php
index a0d03937265..414c86b55f3 100644
--- a/core/modules/file/src/Tests/FileFieldWidgetTest.php
+++ b/core/modules/file/src/Tests/FileFieldWidgetTest.php
@@ -247,32 +247,39 @@ class FileFieldWidgetTest extends FileFieldTestBase {
       $this->assertTrue(empty($node->{$field_name}->target_id), 'Node was successfully saved without any files.');
     }
 
-    $upload_files = array($test_file, $test_file);
+    $upload_files_node_creation = array($test_file, $test_file);
     // Try to upload multiple files, but fewer than the maximum.
-    $nid = $this->uploadNodeFiles($upload_files, $field_name, $type_name);
+    $nid = $this->uploadNodeFiles($upload_files_node_creation, $field_name, $type_name);
     $node_storage->resetCache(array($nid));
     $node = $node_storage->load($nid);
-    $this->assertEqual(count($node->{$field_name}), count($upload_files), 'Node was successfully saved with mulitple files.');
+    $this->assertEqual(count($node->{$field_name}), count($upload_files_node_creation), 'Node was successfully saved with mulitple files.');
 
     // Try to upload more files than allowed on revision.
-    $this->uploadNodeFiles($upload_files, $field_name, $nid, 1);
-    $args = array(
+    $upload_files_node_revision = array($test_file, $test_file, $test_file, $test_file);
+    $this->uploadNodeFiles($upload_files_node_revision, $field_name, $nid, 1);
+    $args = [
       '%field' => $field_name,
-      '@count' => $cardinality
-    );
-    $this->assertRaw(t('%field: this field cannot hold more than @count values.', $args));
+      '@max' => $cardinality,
+      '@count' => count($upload_files_node_creation) + count($upload_files_node_revision),
+      '%list' => implode(', ', array_fill(0, 3, $test_file->getFilename())),
+    ];
+    $this->assertRaw(t('Field %field can only hold @max values but there were @count uploaded. The following files have been omitted as a result: %list.', $args));
     $node_storage->resetCache(array($nid));
     $node = $node_storage->load($nid);
-    $this->assertEqual(count($node->{$field_name}), count($upload_files), 'More files than allowed could not be saved to node.');
+    $this->assertEqual(count($node->{$field_name}), $cardinality, 'More files than allowed could not be saved to node.');
 
-    // Try to upload exactly the allowed number of files on revision.
-    $this->uploadNodeFile($test_file, $field_name, $nid, 1);
+    // Try to upload exactly the allowed number of files on revision. Create an
+    // empty node first, to fill it in its first revision.
+    $node = $this->drupalCreateNode([
+      'type' => $type_name
+    ]);
+    $this->uploadNodeFile($test_file, $field_name, $node->id(), 1);
     $node_storage->resetCache(array($nid));
     $node = $node_storage->load($nid);
     $this->assertEqual(count($node->{$field_name}), $cardinality, 'Node was successfully revised to maximum number of files.');
 
     // Try to upload exactly the allowed number of files, new node.
-    $upload_files[] = $test_file;
+    $upload_files = array_fill(0, $cardinality, $test_file);
     $nid = $this->uploadNodeFiles($upload_files, $field_name, $type_name);
     $node_storage->resetCache(array($nid));
     $node = $node_storage->load($nid);