diff -u b/core/modules/node/src/Controller/NodeController.php b/core/modules/node/src/Controller/NodeController.php
--- b/core/modules/node/src/Controller/NodeController.php
+++ b/core/modules/node/src/Controller/NodeController.php
@@ -213,7 +213,7 @@
               '#type' => 'inline_template',
               '#template' => '{{ old_revision_message }}',
               '#context' => array(
-                'old_revision_message' => $this->t('!date by !username !revision-log'
+                'old_revision_message' => $this->t('!date by !username !revision-log',
                   array(
                     '!date' => $this->l($this->dateFormatter->format($revision->revision_timestamp->value, 'short'), new Url('node.revision_show', array('node' => $node->id(), 'node_revision' => $vid))),
                     '!username' => \Drupal::service('renderer')->render($username),