diff --git a/nanoc/lib/mixin.rb b/nanoc/lib/mixin.rb
index 7e2acc8..3b7608c 100644
--- a/nanoc/lib/mixin.rb
+++ b/nanoc/lib/mixin.rb
@@ -15,7 +15,7 @@ module Mixin
   end
 
   def revision
-    cmd("git rev-parse HEAD").stdout.strip
+    @rev ||= cmd("git", "rev-parse", "HEAD").stdout.strip
   end
 
   def build_dir
diff --git a/nanoc/lib/mixin/opengraph.rb b/nanoc/lib/mixin/opengraph.rb
index c23e757..e9fd834 100644
--- a/nanoc/lib/mixin/opengraph.rb
+++ b/nanoc/lib/mixin/opengraph.rb
@@ -12,7 +12,7 @@ module Mixin::OpenGraph
       {title: t(context.locale, "TheNobleQuran"),
        description: surah.name,
        url: "#{base_url}/#{context.locale}/#{surah.slug}/",
-       image: "#{base_url}/images/og/#{surah.id}.png"}
+       image: "#{base_url}/images/og/#{surah.id}.png?v=#{revision}"}
     when "redirect.html.erb", "surah-index.html.erb"
       {title: t(context.locale, "TheNobleQuran"),
        description: t(context.locale, "meta.index.description"),