diff --git a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs
index 1a214fa1..1b187b5f 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientEventExtensions.cs
@@ -286,7 +286,7 @@ namespace SKIT.FlurlHttpClient.Wechat.Api
             if (callbackNonce == null) throw new ArgumentNullException(nameof(callbackNonce));
             if (callbackSignature == null) throw new ArgumentNullException(nameof(callbackSignature));
 
-            ISet<string> set = new SortedSet<string>() { client.Credentials.PushToken!, callbackTimestamp, callbackNonce };
+            ISet<string> set = new SortedSet<string>(StringComparer.Ordinal) { client.Credentials.PushToken!, callbackTimestamp, callbackNonce };
             string sign = Security.SHA1Utility.Hash(string.Concat(set));
             return string.Equals(sign, callbackSignature, StringComparison.InvariantCultureIgnoreCase);
         }
diff --git a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs
index 6f8cee46..1b06da87 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.Api/Extensions/WechatApiClientParameterExtensions.cs
@@ -60,7 +60,7 @@ namespace SKIT.FlurlHttpClient.Wechat.Api
             string nonce = Guid.NewGuid().ToString("N");
             string cardType = "INVOICE";
 
-            SortedSet<string> sortedParams = new SortedSet<string>();
+            ISet<string> sortedParams = new SortedSet<string>(StringComparer.Ordinal);
             sortedParams.Add(cardType);
             sortedParams.Add(timestamp);
             sortedParams.Add(client.Credentials.AppId);
diff --git a/src/SKIT.FlurlHttpClient.Wechat.Api/Utilities/WxBizMsgCryptor.cs b/src/SKIT.FlurlHttpClient.Wechat.Api/Utilities/WxBizMsgCryptor.cs
index 926026b8..5224bc6b 100644
--- a/src/SKIT.FlurlHttpClient.Wechat.Api/Utilities/WxBizMsgCryptor.cs
+++ b/src/SKIT.FlurlHttpClient.Wechat.Api/Utilities/WxBizMsgCryptor.cs
@@ -231,7 +231,7 @@ namespace SKIT.FlurlHttpClient.Wechat.Api.Utilities
             if (sNonce == null) throw new ArgumentNullException(nameof(sNonce));
             if (sMsgEncrypt == null) throw new ArgumentNullException(nameof(sMsgEncrypt));
 
-            ISet<string> set = new SortedSet<string>();
+            ISet<string> set = new SortedSet<string>(StringComparer.Ordinal);
             set.Add(sToken);
             set.Add(sTimestamp);
             set.Add(sNonce);