diff --git a/src/OrchardCore.Modules/OrchardCore.Contents/Sitemaps/ContentTypesSitemapSourceBuilder.cs b/src/OrchardCore.Modules/OrchardCore.Contents/Sitemaps/ContentTypesSitemapSourceBuilder.cs
index 2f3267480f9..142587e5e05 100644
--- a/src/OrchardCore.Modules/OrchardCore.Contents/Sitemaps/ContentTypesSitemapSourceBuilder.cs
+++ b/src/OrchardCore.Modules/OrchardCore.Contents/Sitemaps/ContentTypesSitemapSourceBuilder.cs
@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
@@ -74,15 +73,15 @@ private async Task<bool> BuildUrlsetMetadataAsync(ContentTypesSitemapSource sour
 
         private async Task<bool> BuildExtendedMetadataAsync(SitemapBuilderContext context, ContentItemsQueryContext queryContext, ContentItem contentItem, XElement url)
         {
-            var suceeded = true;
+            var succeeded = true;
             foreach (var sc in _sitemapContentItemExtendedMetadataProviders)
             {
                 if (!await sc.ApplyExtendedMetadataAsync(context, queryContext, contentItem, url))
                 {
-                    suceeded = false;
+                    succeeded = false;
                 }
             }
-            return suceeded;
+            return succeeded;
         }
 
         private async Task<bool> BuildUrlAsync(SitemapBuilderContext context, ContentItem contentItem, XElement url)
@@ -162,7 +161,7 @@ private static void PopulateLastMod(ContentItem contentItem, XElement url)
             if (contentItem.ModifiedUtc.HasValue)
             {
                 var lastMod = new XElement(_namespace + "lastmod");
-                lastMod.Add(contentItem.ModifiedUtc.GetValueOrDefault().ToString("yyyy-MM-ddTHH:mm:sszzz"));
+                lastMod.Add(contentItem.ModifiedUtc.GetValueOrDefault().ToString("yyyy-MM-ddTHH:mm:sszzz", CultureInfo.InvariantCulture));
                 url.Add(lastMod);
             }
         }