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..d1b443c 100644
--- a/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/File/ReadOnlyStreamWrapperTest.php
@@ -56,6 +56,10 @@ function testWriteFunctions() {
     // Attempt to open a file in write mode
     $handle = @fopen($uri, 'w+');
     $this->assertFalse($handle, 'Unable to open a file for writing 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 binary mode with the read-only stream wrapper.');
+    $this->assertTrue(fclose($handle), 'Able to close file opened in binary mode using the read_only stream wrapper.');
     // 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.');
@@ -72,7 +76,7 @@ function testWriteFunctions() {
     // Attempt to flush output to the file
     $this->assertFalse(@fflush($handle), 'Unable to flush output to file using the read-only stream wrapper.');
     // Attempt to close the stream.  (Suppress errors, as fclose triggers fflush.)
-    $this->assertTrue(@fclose($handle), 'Able to close file using the read_only stream wrapper.');
+    $this->assertTrue(fclose($handle), 'Able to close file using the read_only stream wrapper.');
     // Test the rename() function
     $this->assertFalse(@rename($uri, $this->scheme . '://newname.txt'), 'Unable to rename files using the read-only stream wrapper.');
     // Test the unlink() function