diff --git a/website/presentation/default.nix b/website/presentation/default.nix
index aa0dba4..7c472dd 100644
--- a/website/presentation/default.nix
+++ b/website/presentation/default.nix
@@ -49,7 +49,10 @@ in
         head = ''
           <title>${page.title}</title>
           <meta name="description" content="${page.description}" />
-          <meta name="author" content="${with lib; if isList page.author then join ", " page.author else page.author}" />
+          ${with lib; join "\n" (map
+          (author: ''<meta name="author" content="${author}" />'')
+          (if isList page.author then page.author else [page.author]))
+          }
         '';
         body = ''
           ${templates.nav { menu = { menu = config.menus.main; }; }}
diff --git a/website/structure/content-types.nix b/website/structure/content-types.nix
index d396010..cd9a471 100644
--- a/website/structure/content-types.nix
+++ b/website/structure/content-types.nix
@@ -95,12 +95,12 @@ in
         };
         date = mkOption {
           description = "Publication date";
-          type = with types; nullOr str;
+          type = with types; str;
           default = null;
         };
         author = mkOption {
           description = "Page author";
-          type = with types; nullOr (either str (listOf str));
+          type = with types; either str (nonEmptyListOf str);
           default = null;
         };
       };