diff --git a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientExecuteCgibinMidasExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientExecuteCgibinMidasExtensions.cs
index cc8b8707..9c178394 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientExecuteCgibinMidasExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientExecuteCgibinMidasExtensions.cs
@@ -40,7 +40,7 @@ namespace SKIT.FlurlHttpClient.Wechat.Api
                         { "offer_id", HttpUtility.UrlEncode(request.MidasOfferId ?? string.Empty) },
                         { "zone_id", HttpUtility.UrlEncode(request.MidasZoneId ?? string.Empty) },
                         { "pf", HttpUtility.UrlEncode(request.Platform ?? string.Empty) },
-                        { "ts", request.Timestamp.ToString() }
+                        { "ts", request.Timestamp.ToString()! }
                     }
                 );
                 string plainText = string.Join("&", paramMap.Select(e => $"{e.Key}={e.Value}"))
diff --git a/src/SKIT.FlurlHttpClient.Wechat.Work/Utilities/WxBizMsgCryptor.cs b/src/SKIT.FlurlHttpClient.Wechat.Work/Utilities/WxBizMsgCryptor.cs
index 81f9d879..b20002e8 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.Work/Utilities/WxBizMsgCryptor.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.Work/Utilities/WxBizMsgCryptor.cs
@@ -275,7 +275,10 @@ namespace SKIT.FlurlHttpClient.Wechat.Work.Utilities
                 XmlDocument xmlDoc = new XmlDocument();
                 xmlDoc.LoadXml(xml);
 
-                XmlNode xmlRoot = xmlDoc.FirstChild;
+                XmlNode? xmlRoot = xmlDoc.FirstChild;
+                if (xmlRoot == null)
+                    return false;
+
                 encryptedMsg = xmlRoot["Encrypt"]?.InnerText?.ToString();
                 toUserName = xmlRoot["ToUserName"]?.InnerText?.ToString();
                 agentId = xmlRoot["AgentID"]?.InnerText?.ToString();