diff --git a/lib/template.html b/lib/template.html
index 38e89f6..c06665c 100755
--- a/lib/template.html
+++ b/lib/template.html
@@ -111,7 +111,7 @@
   <meta name="author" content="{{ seo_author_name }}" />
 {% endif %}
 
-<meta property="og:locale" content="{{ seo_page_lang }}" />
+<meta property="og:locale" content="{{ seo_page_lang | replace:'-','_' }}" />
 
 {% if seo_description %}
   <meta name="description" content="{{ seo_description }}" />
@@ -128,7 +128,6 @@
 {% endif %}
 
 {% if seo_page_image %}
-
   <meta property="og:image" content="{{ seo_page_image }}" />
   {% if page.image.height %}
     <meta property="og:image:height" content="{{ page.image.height }}" />
diff --git a/spec/jekyll_seo_tag_spec.rb b/spec/jekyll_seo_tag_spec.rb
index f738072..a96aea2 100755
--- a/spec/jekyll_seo_tag_spec.rb
+++ b/spec/jekyll_seo_tag_spec.rb
@@ -606,5 +606,14 @@ EOS
         end
       end
     end
+    
+    context "with site.lang hyphenated" do
+      let(:site)  { make_site("lang" => "en-US") }
+
+      it "coerces hyphen to underscore" do
+        expected = %r!<meta property="og:locale" content="en_US" />!
+        expect(output).to match(expected)
+      end
+    end
   end
 end