diff --git a/assets/css/default.css b/assets/css/default.css
index 00881253..4d6c6c2f 100644
--- a/assets/css/default.css
+++ b/assets/css/default.css
@@ -197,6 +197,7 @@ img.thumbnail {
   display: block; /* See: https://stackoverflow.com/a/11635197 */
   width: 100%;
   object-fit: cover;
+  aspect-ratio: 16 / 9;
 }
 
 .thumbnail-placeholder {