diff -u b/core/modules/file/file.module b/core/modules/file/file.module
--- b/core/modules/file/file.module
+++ b/core/modules/file/file.module
@@ -294,8 +294,10 @@
 
       // Allow a mixed result of messages and errors so validators can
       // provide messages to be shown only if there are no errors.
-      if (array_key_exists('errors', $result)) {
-        $errors = array_merge($errors, $result['errors']);
+      if (array_intersect(['errors', 'messages'], array_keys($result))) {
+        if (array_key_exists('errors', $result)) {
+          $errors = array_merge($errors, $result['errors']);
+        }
         if (array_key_exists('messages', $result)) {
           $messages = array_merge($messages, $result['messages']);
         }
only in patch2:
unchanged:
--- a/core/modules/file/tests/src/Kernel/ValidatorTest.php
+++ b/core/modules/file/tests/src/Kernel/ValidatorTest.php
@@ -70,20 +70,20 @@ function testFileValidateIsImage() {
    */
   function testFileValidateImageResolution() {
     // Non-images.
-    $errors = file_validate_image_resolution($this->nonImage);
-    $this->assertEqual(count($errors), 0, 'Should not get any errors for a non-image file.', 'File');
-    $errors = file_validate_image_resolution($this->nonImage, '50x50', '100x100');
-    $this->assertEqual(count($errors), 0, 'Do not check the resolution on non files.', 'File');
+    $result = file_validate_image_resolution($this->nonImage);
+    $this->assertEqual(count($result['errors']), 0, 'Should not get any errors for a non-image file.', 'File');
+    $result = file_validate_image_resolution($this->nonImage, '50x50', '100x100');
+    $this->assertEqual(count($result['errors']), 0, 'Do not check the resolution on non files.', 'File');
 
     // Minimum size.
-    $errors = file_validate_image_resolution($this->image);
-    $this->assertEqual(count($errors), 0, 'No errors for an image when there is no minimum or maximum resolution.', 'File');
-    $errors = file_validate_image_resolution($this->image, 0, '200x1');
-    $this->assertEqual(count($errors), 1, 'Got an error for an image that was not wide enough.', 'File');
-    $errors = file_validate_image_resolution($this->image, 0, '1x200');
-    $this->assertEqual(count($errors), 1, 'Got an error for an image that was not tall enough.', 'File');
-    $errors = file_validate_image_resolution($this->image, 0, '200x200');
-    $this->assertEqual(count($errors), 1, 'Small images report an error.', 'File');
+    $result = file_validate_image_resolution($this->image);
+    $this->assertEqual(count($result['errors']), 0, 'No errors for an image when there is no minimum or maximum resolution.', 'File');
+    $result = file_validate_image_resolution($this->image, 0, '200x1');
+    $this->assertEqual(count($result['errors']), 1, 'Got an error for an image that was not wide enough.', 'File');
+    $result = file_validate_image_resolution($this->image, 0, '1x200');
+    $this->assertEqual(count($result['errors']), 1, 'Got an error for an image that was not tall enough.', 'File');
+    $result = file_validate_image_resolution($this->image, 0, '200x200');
+    $this->assertEqual(count($result['errors']), 1, 'Small images report an error.', 'File');
 
     // Maximum size.
     if ($this->container->get('image.factory')->getToolkitId()) {
@@ -91,8 +91,8 @@ function testFileValidateImageResolution() {
       copy('core/misc/druplicon.png', 'temporary://druplicon.png');
       $this->image->setFileUri('temporary://druplicon.png');
 
-      $errors = file_validate_image_resolution($this->image, '10x5');
-      $this->assertEqual(count($errors), 0, 'No errors should be reported when an oversized image can be scaled down.', 'File');
+      $result = file_validate_image_resolution($this->image, '10x5');
+      $this->assertEqual(count($result['errors']), 0, 'No errors should be reported when an oversized image can be scaled down.', 'File');
 
       $image = $this->container->get('image.factory')->get($this->image->getFileUri());
       $this->assertTrue($image->getWidth() <= 10, 'Image scaled to correct width.', 'File');
@@ -101,15 +101,15 @@ function testFileValidateImageResolution() {
       // Once again, now with negative width and height to force an error.
       copy('core/misc/druplicon.png', 'temporary://druplicon.png');
       $this->image->setFileUri('temporary://druplicon.png');
-      $errors = file_validate_image_resolution($this->image, '-10x-5');
-      $this->assertEqual(count($errors), 1, 'An error reported for an oversized image that can not be scaled down.', 'File');
+      $result = file_validate_image_resolution($this->image, '-10x-5');
+      $this->assertEqual(count($result['errors']), 1, 'An error reported for an oversized image that can not be scaled down.', 'File');
 
       drupal_unlink('temporary://druplicon.png');
     }
     else {
       // TODO: should check that the error is returned if no toolkit is available.
-      $errors = file_validate_image_resolution($this->image, '5x10');
-      $this->assertEqual(count($errors), 1, 'Oversize images that cannot be scaled get an error.', 'File');
+      $result = file_validate_image_resolution($this->image, '5x10');
+      $this->assertEqual(count($result['errors']), 1, 'Oversize images that cannot be scaled get an error.', 'File');
     }
   }