diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
index a088a8b..406d06f 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
@@ -97,7 +97,6 @@ public function buildByExtension($extension) {
       }
       else {
         $message = sprintf('The extension "%s" is not available.', $extension);
-        assert(false, $message);
         trigger_error($message, E_USER_WARNING);
         return;
       }
diff --git a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
index b4186a5..9437784 100644
--- a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
@@ -191,16 +191,11 @@ public function testMissingExtension() {
       ->with('missing_extension')
       ->will($this->returnValue(FALSE));
 
-    assert_options(ASSERT_ACTIVE, 0);
     set_error_handler(function($severity, $message, $file, $line) {
       $this->assertEquals($message, 'The extension "missing_extension" is not available.');
     });
     $this->assertEquals(NULL, $this->libraryDiscoveryParser->buildByExtension('missing_extension'), 'The extension "missing_extension" is not available');
     restore_error_handler();
-
-    assert_options(ASSERT_ACTIVE, 1);
-    $this->setExpectedException('\AssertionError', 'The extension "missing_extension" is not available.');
-    $this->libraryDiscoveryParser->buildByExtension('missing_extension');
   }
 
   /**