diff --git a/core/lib/Drupal/Core/StreamWrapper/LocalReadOnlyStream.php b/core/lib/Drupal/Core/StreamWrapper/LocalReadOnlyStream.php
index 1b14280..b532846 100644
--- a/core/lib/Drupal/Core/StreamWrapper/LocalReadOnlyStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/LocalReadOnlyStream.php
@@ -40,7 +40,7 @@
    * @see http://php.net/manual/streamwrapper.stream-open.php
    */
   public function stream_open($uri, $mode, $options, &$opened_path) {
-    if ($mode != "r") {
+    if ($mode !== 'r' && $mode !== 'rb') {
       if ($options & STREAM_REPORT_ERRORS) {
         trigger_error('stream_open() write modes not supported for read-only stream wrappers', E_USER_WARNING);
       }
diff --git a/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php b/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
index 909fe1c..c862291 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
@@ -59,6 +59,9 @@ function testWriteFunctions() {
     // Attempt to open a file in read mode
     $handle = fopen($uri, 'r');
     $this->assertTrue($handle, 'Able to open a file for reading with the read-only stream wrapper.');
+    // Attempt to open a file in binary read mode
+    $handle = fopen($uri, 'rb');
+    $this->assertTrue($handle, 'Able to open a file for reading in bibary mode with the read-only stream wrapper.');
     // Attempt to change file permissions
     $this->assertFalse(@drupal_chmod($uri, 0777), 'Unable to change file permissions when using read-only stream wrapper.');
     // Attempt to acquire an exclusive lock for writing