diff --git a/layouts/_default/baseof.html b/layouts/_default/baseof.html
index 2c7955239..1bd0f178c 100644
--- a/layouts/_default/baseof.html
+++ b/layouts/_default/baseof.html
@@ -49,7 +49,7 @@
 
 <html itemscope itemtype="https://schema.org/WebPage" class="no-js" lang="{{ .Site.Language.Lang }}">
 
-<head>
+<head prefix="og: http://ogp.me/ns#">
     <meta charset="utf-8">
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <meta name="siteBaseUrl" content="{{ .Site.BaseURL }}">
