diff --git a/src/Orchard.Web/Modules/Orchard.MultiTenancy/Services/TenantService.cs b/src/Orchard.Web/Modules/Orchard.MultiTenancy/Services/TenantService.cs
index 0e6a33ee6..08e7376ee 100644
--- a/src/Orchard.Web/Modules/Orchard.MultiTenancy/Services/TenantService.cs
+++ b/src/Orchard.Web/Modules/Orchard.MultiTenancy/Services/TenantService.cs
@@ -48,7 +48,7 @@ namespace Orchard.MultiTenancy.Services {
 
                 ExtensionDescriptor theme = descriptor;
 
-                if (!theme.Tags.Contains("hidden")) {
+                if (theme.Tags == null || !theme.Tags.Contains("hidden")) {
                     themes.Add(theme);
                 }
             }