diff --git a/core/modules/views/tests/src/Kernel/ViewsPreprocessTest.php b/core/modules/views/tests/src/Kernel/ViewsPreprocessTest.php
index b1be143718..a8c4a82194 100644
--- a/core/modules/views/tests/src/Kernel/ViewsPreprocessTest.php
+++ b/core/modules/views/tests/src/Kernel/ViewsPreprocessTest.php
@@ -42,13 +42,13 @@ public function testCssClassCleaning() {
     $view = Views::getview('test_preprocess');
     $build = $view->buildRenderable();
     $renderer->renderRoot($build);
-    $this->assertContains('class="entity-test__default', (string) $build['#markup']);
+    $this->assertContains('class="entity-test--default entity-test__default', (string) $build['#markup']);
     $view->destroy();
 
     $view->setDisplay('display_2');
     $build = $view->buildRenderable();
     $renderer->renderRoot($build);
-    $this->assertContains('class="entity-test__default and-another-class', (string) $build['#markup']);
+    $this->assertContains('class="entity-test--default and-another-class entity-test__default', (string) $build['#markup']);
   }
 
 }
diff --git a/core/modules/views/views.theme.inc b/core/modules/views/views.theme.inc
index 9321da75ac..482131f522 100644
--- a/core/modules/views/views.theme.inc
+++ b/core/modules/views/views.theme.inc
@@ -34,10 +34,14 @@ function template_preprocess_views_view(&$variables) {
 
   $css_class = $view->display_handler->getOption('css_class');
   if (!empty($css_class)) {
-    $css_classes = explode(' ', strip_tags($css_class));
-    foreach ($css_classes as $class) {
-      $variables['attributes']['class'][] = Html::cleanCssIdentifier($class);
-    }
+    // Keep backwards compatibility of old sanitised classes and variables.
+    $variables['css_class'] = preg_replace('/[^a-zA-Z0-9- ]/', '-', $css_class);
+    $variables['attributes']['class'][] = $variables['css_class'];
+    // Add properly sanitised classes.
+    $css_classes = array_map('\Drupal\Component\Utility\Html::cleanCssIdentifier', explode(' ', $css_class));
+    // Merge the BC classes with the properly sanitised classes and remove
+    // duplicates.
+    $variables['attributes']['class'] = array_unique(array_merge($variables['attributes']['class'], $css_classes));
   }
 
   // contextual_preprocess() only works on render elements, and since this theme