diff --git a/DotNetCasClient/Utils/UrlUtil.cs b/DotNetCasClient/Utils/UrlUtil.cs
index 6f95c6b..bc3c470 100644
--- a/DotNetCasClient/Utils/UrlUtil.cs
+++ b/DotNetCasClient/Utils/UrlUtil.cs
@@ -139,7 +139,7 @@ public static string ConstructValidateUrl(string serviceTicket, bool gateway, bo
 
             EnhancedUriBuilder ub = new EnhancedUriBuilder(EnhancedUriBuilder.Combine(CasAuthentication.CasServerUrlPrefix, CasAuthentication.TicketValidator.UrlSuffix));
             ub.QueryItems.Add(CasAuthentication.TicketValidator.ServiceParameterName, HttpUtility.UrlEncode(ConstructServiceUrl(gateway)));
-            ub.QueryItems.Add(CasAuthentication.TicketValidator.ArtifactParameterName, serviceTicket);
+            ub.QueryItems.Add(CasAuthentication.TicketValidator.ArtifactParameterName, HttpUtility.UrlEncode(serviceTicket));
 
             if (renew)
             {