diff --git a/core/lib/Drupal/Core/Template/AttributeArray.php b/core/lib/Drupal/Core/Template/AttributeArray.php
index c432ba0..dbe8089 100644
--- a/core/lib/Drupal/Core/Template/AttributeArray.php
+++ b/core/lib/Drupal/Core/Template/AttributeArray.php
@@ -66,6 +66,8 @@ public function offsetExists($offset) {
    * Implements the magic __toString() method.
    */
   public function __toString() {
+    // Filter out any empty values before printing.
+    $this->value = array_filter($this->value);
     return String::checkPlain(implode(' ', $this->value));
   }
 
diff --git a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
index bcd04a2..113fd79 100644
--- a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
@@ -148,20 +148,21 @@ public function testTwigAddRemoveClasses($template, $expected, $seed_attributes
    *   a resulting string of classes and an optional array of attributes.
    */
   public function providerTestAttributeClassHelpers() {
+    // The empty array elements check that blank class names are filtered out when printed.
     return array(
       array("{{ attributes.class }}", ''),
       array("{{ attributes.addClass('everest').class }}", 'everest'),
-      array("{{ attributes.addClass(['k2', 'kangchenjunga']).class }}", 'k2 kangchenjunga'),
-      array("{{ attributes.addClass('lhotse', 'makalu', 'cho-oyu').class }}", 'lhotse makalu cho-oyu'),
+      array("{{ attributes.addClass(['k2', 'kangchenjunga', '']).class }}", 'k2 kangchenjunga'),
+      array("{{ attributes.addClass('lhotse', 'makalu', 'cho-oyu', '').class }}", 'lhotse makalu cho-oyu'),
       array(
         "{{ attributes.addClass('nanga-parbat').class }}",
         'dhaulagiri manaslu nanga-parbat',
-        array('class' => array('dhaulagiri', 'manaslu')),
+        array('class' => array('dhaulagiri', 'manaslu', '')),
       ),
       array(
         "{{ attributes.removeClass('annapurna').class }}",
         'gasherbrum-i',
-        array('class' => array('annapurna', 'gasherbrum-i')),
+        array('class' => array('annapurna', 'gasherbrum-i', '')),
       ),
       array(
         "{{ attributes.removeClass(['broad peak']).class }}",