diff --git a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
index ad54a2c..eb78696 100644
--- a/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
+++ b/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
@@ -139,7 +139,7 @@ public function buildByExtension($extension) {
                 continue;
               }
               // Files are are in $category and $files is empty.
-              else if (empty($files)) {
+              else {
                 throw new InvalidCssDefinitionException(sprintf("Every CSS asset must be nested under a SMACSS category in the %s.library.yml file ('%s' seems to be a file name, allowed categories are Base, Layout, Component, State, Theme)", $extension, $category));
               }
             }