diff --git a/core/includes/file.inc b/core/includes/file.inc
index 6065dd4..ba09b9c 100644
--- a/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -1275,17 +1275,14 @@ function file_get_mimetype($uri, $mapping = NULL) {
  */
 function drupal_chmod($uri, $mode = NULL) {
   if (!isset($mode)) {
-    // Configuration system stores default modes as strings. We use octdec() so
-    // that the octal permission numbers can be expressed as integers or strings
-    // and will be converted correctly in both cases.
     if (is_dir($uri)) {
-      $mode = octdec(\Drupal::config('system.file')->get('chmod.directory'));
+      $mode = \Drupal::config('system.file')->get('chmod.directory');
       if (!$mode) {
         $mode = 0775;
       }
     }
     else {
-      $mode = octdec(\Drupal::config('system.file')->get('chmod.file'));
+      $mode = \Drupal::config('system.file')->get('chmod.file');
       if (!$mode) {
         $mode = 0664;
       }
@@ -1463,7 +1460,7 @@ function drupal_mkdir($uri, $mode = NULL, $recursive = FALSE, $context = NULL) {
     $mode = FALSE;
     // During early update there's no container.
     if (is_object(\Drupal::getContainer())) {
-      $mode = octdec(\Drupal::config('system.file')->get('chmod.directory'));
+      $mode = \Drupal::config('system.file')->get('chmod.directory');
     }
     if (!$mode) {
       $mode = 0775;
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php b/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php
index 7fd19c5..eef3373 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/DirectoryTest.php
@@ -89,7 +89,7 @@ function testFileCheckDirectoryHandling() {
     }
 
     // Test that the directory has the correct permissions.
-    $this->assertDirectoryPermissions($directory, octdec(\Drupal::config('system.file')->get('chmod.directory')));
+    $this->assertDirectoryPermissions($directory, \Drupal::config('system.file')->get('chmod.directory'));
 
     // Remove .htaccess file to then test that it gets re-created.
     @drupal_unlink(file_default_scheme() . '://.htaccess');
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php b/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
index 540c19a..30973ad 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/FileTestBase.php
@@ -82,11 +82,6 @@ function assertSameFile(FileInterface $file1, FileInterface $file2) {
    *   Optional message.
    */
   function assertFilePermissions($filepath, $expected_mode, $message = NULL) {
-    // Configuration system stores default modes as strings.
-    if (is_string($expected_mode)) {
-      // Convert string to octal.
-      $expected_mode = octdec($expected_mode);
-    }
     // Clear out PHP's file stat cache to be sure we see the current value.
     clearstatcache(TRUE, $filepath);
 
@@ -122,11 +117,6 @@ function assertFilePermissions($filepath, $expected_mode, $message = NULL) {
    *   Optional message.
    */
   function assertDirectoryPermissions($directory, $expected_mode, $message = NULL) {
-    // Configuration system stores default modes as strings.
-    if (is_string($expected_mode)) {
-      // Convert string to octal.
-      $expected_mode = octdec($expected_mode);
-    }
     // Clear out PHP's file stat cache to be sure we see the current value.
     clearstatcache(TRUE, $directory);
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedCopyTest.php b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedCopyTest.php
index 70f1903..b9e4308 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedCopyTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedCopyTest.php
@@ -34,7 +34,7 @@ function testNormal() {
     $this->assertEqual($new_filepath, $desired_filepath, 'Returned expected filepath.');
     $this->assertTrue(file_exists($uri), 'Original file remains.');
     $this->assertTrue(file_exists($new_filepath), 'New file exists.');
-    $this->assertFilePermissions($new_filepath, octdec($config->get('chmod.file')));
+    $this->assertFilePermissions($new_filepath, $config->get('chmod.file'));
 
     // Copying with rename.
     $desired_filepath = 'public://' . $this->randomName();
@@ -44,7 +44,7 @@ function testNormal() {
     $this->assertNotEqual($newer_filepath, $desired_filepath, 'Returned expected filepath.');
     $this->assertTrue(file_exists($uri), 'Original file remains.');
     $this->assertTrue(file_exists($newer_filepath), 'New file exists.');
-    $this->assertFilePermissions($newer_filepath, octdec($config->get('chmod.file')));
+    $this->assertFilePermissions($newer_filepath, $config->get('chmod.file'));
 
     // TODO: test copying to a directory (rather than full directory/file path)
     // TODO: test copying normal files using normal paths (rather than only streams)
@@ -75,7 +75,7 @@ function testOverwriteSelf() {
     $this->assertNotEqual($new_filepath, $uri, 'Copied file has a new name.');
     $this->assertTrue(file_exists($uri), 'Original file exists after copying onto itself.');
     $this->assertTrue(file_exists($new_filepath), 'Copied file exists after copying onto itself.');
-    $this->assertFilePermissions($new_filepath, octdec($config->get('chmod.file')));
+    $this->assertFilePermissions($new_filepath, $config->get('chmod.file'));
 
     // Copy the file onto itself without renaming fails.
     $new_filepath = file_unmanaged_copy($uri, $uri, FILE_EXISTS_ERROR);
@@ -93,6 +93,6 @@ function testOverwriteSelf() {
     $this->assertNotEqual($new_filepath, $uri, 'Copied file has a new name.');
     $this->assertTrue(file_exists($uri), 'Original file exists after copying onto itself.');
     $this->assertTrue(file_exists($new_filepath), 'Copied file exists after copying onto itself.');
-    $this->assertFilePermissions($new_filepath, octdec($config->get('chmod.file')));
+    $this->assertFilePermissions($new_filepath, $config->get('chmod.file'));
   }
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedMoveTest.php b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedMoveTest.php
index 1503bd1..5901a9d 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedMoveTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedMoveTest.php
@@ -34,7 +34,7 @@ function testNormal() {
     $this->assertEqual($new_filepath, $desired_filepath, 'Returned expected filepath.');
     $this->assertTrue(file_exists($new_filepath), 'File exists at the new location.');
     $this->assertFalse(file_exists($uri), 'No file remains at the old location.');
-    $this->assertFilePermissions($new_filepath, octdec($config->get('chmod.file')));
+    $this->assertFilePermissions($new_filepath, $config->get('chmod.file'));
 
     // Moving with rename.
     $desired_filepath = 'public://' . $this->randomName();
@@ -45,7 +45,7 @@ function testNormal() {
     $this->assertNotEqual($newer_filepath, $desired_filepath, 'Returned expected filepath.');
     $this->assertTrue(file_exists($newer_filepath), 'File exists at the new location.');
     $this->assertFalse(file_exists($new_filepath), 'No file remains at the old location.');
-    $this->assertFilePermissions($newer_filepath, octdec($config->get('chmod.file')));
+    $this->assertFilePermissions($newer_filepath, $config->get('chmod.file'));
 
     // TODO: test moving to a directory (rather than full directory/file path)
     // TODO: test creating and moving normal files (rather than streams)
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php
index 043ed6c..1b03d13 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/UnmanagedSaveDataTest.php
@@ -36,6 +36,6 @@ function testFileSaveData() {
     $this->assertTrue($filepath, 'Unnamed file saved correctly.');
     $this->assertEqual('asdf.txt', drupal_basename($filepath), 'File was named correctly.');
     $this->assertEqual($contents, file_get_contents($filepath), 'Contents of the file are correct.');
-    $this->assertFilePermissions($filepath, octdec(\Drupal::config('system.file')->get('chmod.file')));
+    $this->assertFilePermissions($filepath, \Drupal::config('system.file')->get('chmod.file'));
   }
 }