diff -u b/core/modules/aggregator/src/Plugin/aggregator/processor/DefaultProcessor.php b/core/modules/aggregator/src/Plugin/aggregator/processor/DefaultProcessor.php
--- b/core/modules/aggregator/src/Plugin/aggregator/processor/DefaultProcessor.php
+++ b/core/modules/aggregator/src/Plugin/aggregator/processor/DefaultProcessor.php
@@ -279,13 +279,13 @@
   }
 
   /**
-   * Normalise MIME type for JPEG.
+   * Normalize MIME type for JPEG.
    *
    * @param string $type
    *   MIME type to normalize.
    *
    * @return string
-   *   Normalised MIME type.
+   *   Normalized MIME type.
    */
   protected function normalizeMimeType($type) {
     return preg_replace('/^image\/jpg$/', 'image/jpeg', $type);