diff --git a/core/includes/errors.inc b/core/includes/errors.inc
index d1b9d16..82e6ebb 100644
--- a/core/includes/errors.inc
+++ b/core/includes/errors.inc
@@ -347,6 +347,10 @@ function format_backtrace(array $backtrace) {
     else {
       $call['function'] = 'main';
     }
+    // Args should never be empty, but it might be if a class method had a
+    // typed parameter, but the use part was not added. Thus, the type of the
+    // parameter would be "unknown" and the class autoloader would have empty
+    // args.
     if (!empty($trace['args'])) {
       foreach ($trace['args'] as $arg) {
         if (is_scalar($arg)) {
diff --git a/core/modules/system/lib/Drupal/system/Tests/Error/FormatBacktraceUnitTest.php b/core/modules/system/lib/Drupal/system/Tests/Error/FormatBacktraceUnitTest.php
index 7eb156d..9b05909 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Error/FormatBacktraceUnitTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Error/FormatBacktraceUnitTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\system\Tests\Common\ValidNumberStepUnitTest.
+ * Contains \Drupal\system\Tests\Common\ValidNumberStepUnitTest.
  */
 
 namespace Drupal\system\Tests\Error;
@@ -13,6 +13,7 @@
  * Tests backtrace formatting by format_backtrace().
  */
 class FormatBacktraceUnitTest extends UnitTestBase {
+
   public static function getInfo() {
     return array(
       'name' => 'Format Backtrace validation',
@@ -64,4 +65,5 @@ function()
     // Compare to the given format.
     $this->assertEqual(format_backtrace($backtrace), $result);
   }
+
 }