diff --git a/src/infrastructure/markup/rule/PhabricatorRemarkupRuleEmbedFile.php b/src/infrastructure/markup/rule/PhabricatorRemarkupRuleEmbedFile.php
index 7a92eada96..3b0acf5b85 100644
--- a/src/infrastructure/markup/rule/PhabricatorRemarkupRuleEmbedFile.php
+++ b/src/infrastructure/markup/rule/PhabricatorRemarkupRuleEmbedFile.php
@@ -50,7 +50,7 @@ final class PhabricatorRemarkupRuleEmbedFile
     $options['name'] = $file_name;
 
     $attrs = array();
-    switch ($options['size']) {
+    switch ((string)$options['size']) {
       case 'full':
         $attrs['src'] = $file->getBestURI();
         $options['image_class'] = null;