diff --git a/static/js/markdown.js b/static/js/markdown.js
index 6f1fc47897..51109290b0 100644
--- a/static/js/markdown.js
+++ b/static/js/markdown.js
@@ -34,7 +34,7 @@ const preview_regexes = [
 
     // Twitter and youtube links are given previews
 
-    /\S*(?:twitter|youtube).com\/\S*/,
+    /\S*(?:twitter|youtube)\.com\/\S*/,
 ];
 
 function contains_preview_link(content) {