diff --git a/core/includes/common.inc b/core/includes/common.inc
index c9913a2..a2e292f 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1801,14 +1801,14 @@ function format_size($size, $langcode = NULL) {
   else {
     $size = $size / DRUPAL_KILOBYTE; // Convert bytes to kilobytes.
     $units = array(
-      t('@size KB', array(), array('langcode' => $langcode)),
-      t('@size MB', array(), array('langcode' => $langcode)),
-      t('@size GB', array(), array('langcode' => $langcode)),
-      t('@size TB', array(), array('langcode' => $langcode)),
-      t('@size PB', array(), array('langcode' => $langcode)),
-      t('@size EB', array(), array('langcode' => $langcode)),
-      t('@size ZB', array(), array('langcode' => $langcode)),
-      t('@size YB', array(), array('langcode' => $langcode)),
+      t('@size KiB', array(), array('langcode' => $langcode)),
+      t('@size MiB', array(), array('langcode' => $langcode)),
+      t('@size GiB', array(), array('langcode' => $langcode)),
+      t('@size TiB', array(), array('langcode' => $langcode)),
+      t('@size PiB', array(), array('langcode' => $langcode)),
+      t('@size EiB', array(), array('langcode' => $langcode)),
+      t('@size ZiB', array(), array('langcode' => $langcode)),
+      t('@size YiB', array(), array('langcode' => $langcode)),
     );
     foreach ($units as $unit) {
       if (round($size, 2) >= DRUPAL_KILOBYTE) {
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/SizeUnitTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/SizeUnitTest.php
index c804d61..97a6848 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/SizeUnitTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/SizeUnitTest.php
@@ -28,21 +28,21 @@ class SizeUnitTest extends UnitTestBase {
     $kb = DRUPAL_KILOBYTE;
     $this->exact_test_cases = array(
       '1 byte' => 1,
-      '1 KB'   => $kb,
-      '1 MB'   => $kb * $kb,
-      '1 GB'   => $kb * $kb * $kb,
-      '1 TB'   => $kb * $kb * $kb * $kb,
-      '1 PB'   => $kb * $kb * $kb * $kb * $kb,
-      '1 EB'   => $kb * $kb * $kb * $kb * $kb * $kb,
-      '1 ZB'   => $kb * $kb * $kb * $kb * $kb * $kb * $kb,
-      '1 YB'   => $kb * $kb * $kb * $kb * $kb * $kb * $kb * $kb,
+      '1 KiB'   => $kb,
+      '1 MiB'   => $kb * $kb,
+      '1 GiB'   => $kb * $kb * $kb,
+      '1 TiB'   => $kb * $kb * $kb * $kb,
+      '1 PiB'   => $kb * $kb * $kb * $kb * $kb,
+      '1 EiB'   => $kb * $kb * $kb * $kb * $kb * $kb,
+      '1 ZiB'   => $kb * $kb * $kb * $kb * $kb * $kb * $kb,
+      '1 YiB'   => $kb * $kb * $kb * $kb * $kb * $kb * $kb * $kb,
     );
     $this->rounded_test_cases = array(
       '2 bytes' => 2,
-      '1 MB' => ($kb * $kb) - 1, // rounded to 1 MB (not 1000 or 1024 kilobyte!)
-      round(3623651 / ($this->exact_test_cases['1 MB']), 2) . ' MB' => 3623651, // megabytes
-      round(67234178751368124 / ($this->exact_test_cases['1 PB']), 2) . ' PB' => 67234178751368124, // petabytes
-      round(235346823821125814962843827 / ($this->exact_test_cases['1 YB']), 2) . ' YB' => 235346823821125814962843827, // yottabytes
+      '1 MiB' => ($kb * $kb) - 1, // rounded to 1 MiB (not 1000 or 1024 kilobyte!)
+      round(3623651 / ($this->exact_test_cases['1 MiB']), 2) . ' MiB' => 3623651, // mebibytes
+      round(67234178751368124 / ($this->exact_test_cases['1 PiB']), 2) . ' PiB' => 67234178751368124, // pebibytes
+      round(235346823821125814962843827 / ($this->exact_test_cases['1 YiB']), 2) . ' YiB' => 235346823821125814962843827, // yobibytes
     );
     parent::setUp();
   }