Show the subtitle if it exists. Custom single still does not seem like it's being loaded, still the theme version?

layouts/_default/single.html

@@ -13,6 +13,9 @@
 
         <article>
             <h2 class="post-title"><a href="{{ .Permalink }}">{{ .Title | markdownify }}</a></h2>
+            {{ if .Params.Subtitle }}
+            <strong>{{ .Params.Subtitle }}</strong>
+            {{ end }}
 
             {{ if .Params.Cover }}
                 <figure class="post-cover">