diff --git a/src/OrchardCore/OrchardCore.ReCaptcha.Core/TagHelpers/ReCaptchaTagHelper.cs b/src/OrchardCore/OrchardCore.ReCaptcha.Core/TagHelpers/ReCaptchaTagHelper.cs
index adaa8f65eae..6737e890a26 100644
--- a/src/OrchardCore/OrchardCore.ReCaptcha.Core/TagHelpers/ReCaptchaTagHelper.cs
+++ b/src/OrchardCore/OrchardCore.ReCaptcha.Core/TagHelpers/ReCaptchaTagHelper.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Globalization;
 using System.Linq;
 using System.Threading.Tasks;