diff --git a/core/modules/file/src/Plugin/Field/FieldType/FileItem.php b/core/modules/file/src/Plugin/Field/FieldType/FileItem.php
index c5fb40b215..636c4ce5b8 100644
--- a/core/modules/file/src/Plugin/Field/FieldType/FileItem.php
+++ b/core/modules/file/src/Plugin/Field/FieldType/FileItem.php
@@ -238,7 +238,7 @@ public static function validateExtensions($element, FormStateInterface $form_sta
       if (!in_array('txt', $extension_array) && !\Drupal::config('system.file')->get('allow_insecure_uploads')) {
         foreach ($extension_array as $extension) {
           if (preg_match(FILE_INSECURE_EXTENSION_REGEX, 'test.' . $extension)) {
-            $form_state->setError($element, t('The extension %extension is insecure. In order to allow it to be uploaded allow the "txt" extension.', ['%extension' => $extension]));
+            $form_state->setError($element, t('The extension %extension is insecure. In order to allow files with this extension to be uploaded add the %txt_extension extension as well.', ['%extension' => $extension, '%txt_extension' => 'txt']));
           }
         }
       }
diff --git a/core/modules/file/src/Tests/FileFieldWidgetTest.php b/core/modules/file/src/Tests/FileFieldWidgetTest.php
index 994a318a8f..7b50e4109a 100644
--- a/core/modules/file/src/Tests/FileFieldWidgetTest.php
+++ b/core/modules/file/src/Tests/FileFieldWidgetTest.php
@@ -352,7 +352,7 @@ public function testFileExtensionsSetting() {
     // By default allowing PHP files without TXT is not permitted.
     $edit = ['settings[file_extensions]' => 'jpg php'];
     $this->drupalPostForm("admin/structure/types/manage/$type_name/fields/$field_id", $edit, t('Save settings'));
-    $this->assertText('The extension php is insecure. In order to allow it to be uploaded allow the "txt" extension.');
+    $this->assertText('The extension php is insecure. In order to allow files with this extension to be uploaded add the txt extension as well.');
 
     // Test allowing PHP and TXT.
     $edit = ['settings[file_extensions]' => 'jpg php txt'];
diff --git a/core/modules/rest/tests/src/Functional/FileUploadResourceTestBase.php b/core/modules/rest/tests/src/Functional/FileUploadResourceTestBase.php
index a5aeef3a51..52aabe86d7 100644
--- a/core/modules/rest/tests/src/Functional/FileUploadResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/FileUploadResourceTestBase.php
@@ -498,8 +498,7 @@ public function testFileUploadMaliciousExtension() {
 
     // Add php as an allowed format without txt. Allow insecure uploads still
     // being FALSE should not allow this.
-    $this->field->setSetting('file_extensions', 'php')
-      ->save();
+    $this->field->setSetting('file_extensions', 'php')->save();
     $this->refreshTestStateAfterRestConfigChange();
 
     $response = $this->fileRequest($uri, $php_string, ['Content-Disposition' => 'filename="example_5.php"']);