diff --git a/public/views/hedgedoc/head.ejs b/public/views/hedgedoc/head.ejs
index 27ecffb7..c6075f6e 100644
--- a/public/views/hedgedoc/head.ejs
+++ b/public/views/hedgedoc/head.ejs
@@ -6,9 +6,9 @@
 <meta name="mobile-web-app-capable" content="yes">
 <%- include('../includes/favicon') %>
 <% for (var og in opengraph) { %>
-<% if (opengraph.hasOwnProperty(og) && String(opengraph[og]).trim() !== '') { %>
+<% if (Object.keys(opengraph).includes(og) && typeof opengraph[og] === 'string' && opengraph[og].trim() !== '') { %>
 <meta property="og:<%= og %>" content="<%= String(opengraph[og]) %>">
-<% }} if (!opengraph.hasOwnProperty('image')) { %>
+<% }} if (!Object.keys(opengraph).includes('image')) { %>
 <meta property="og:image" content="<%- serverURL %>/icons/android-chrome-512x512.png">
 <meta property="og:image:alt" content="HedgeDoc logo">
 <meta property="og:image:type" content="image/png">
diff --git a/public/views/pretty.ejs b/public/views/pretty.ejs
index bddb1db5..dfbb89ce 100644
--- a/public/views/pretty.ejs
+++ b/public/views/pretty.ejs
@@ -15,9 +15,9 @@
     <meta name="description" content="<%= description %>">
     <% } %>
     <% for (var og in opengraph) { %>
-    <% if (opengraph.hasOwnProperty(og) && typeof opengraph[og] === 'string' && opengraph[og].trim() !== '') { %>
+    <% if (Object.keys(opengraph).includes(og) && typeof opengraph[og] === 'string' && opengraph[og].trim() !== '') { %>
     <meta property="og:<%= og %>" content="<%= opengraph[og] %>">
-    <% }} if (!opengraph.hasOwnProperty('image')) { %>
+    <% }} if (!Object.keys(opengraph).includes('image')) { %>
     <meta property="og:image" content="<%- serverURL %>/icons/android-chrome-512x512.png">
     <meta property="og:image:alt" content="HedgeDoc logo">
     <meta property="og:image:type" content="image/png">