diff --git a/dotnet/src/dotnetframework/GxClasses/Domain/GxHttpClient.cs b/dotnet/src/dotnetframework/GxClasses/Domain/GxHttpClient.cs
index 652bf773c..95b3f6863 100644
--- a/dotnet/src/dotnetframework/GxClasses/Domain/GxHttpClient.cs
+++ b/dotnet/src/dotnetframework/GxClasses/Domain/GxHttpClient.cs
@@ -484,13 +484,19 @@ public string get_ProxyHost()
 		{
 			return _proxyHost;
 		}
+#if NETCORE
+		private static Encoding ISO_8859_1 = Encoding.Latin1;
+#else
+		private static Encoding ISO_8859_1 = Encoding.GetEncoding("ISO-8859-1");
+#endif
+		private const string AuthenticationSchemeBasic = "Basic";
 		public void AddAuthentication(int scheme, string realm, string user, string password)
 		{
 			if (scheme >= _Basic && scheme <= _Kerberos)
 				_authCollection.Add(new GxAuthScheme(scheme, realm, user, password));
 			if (scheme == _Basic) {
-				string authHeader = Convert.ToBase64String(Encoding.UTF8.GetBytes($"{user}:{password}"));
-				AddHeader(HttpHeader.AUTHORIZATION, new AuthenticationHeaderValue("Basic", authHeader).ToString());
+				string authHeader = Convert.ToBase64String(ISO_8859_1.GetBytes($"{user}:{password}"));
+				AddHeader(HttpHeader.AUTHORIZATION, new AuthenticationHeaderValue(AuthenticationSchemeBasic, authHeader).ToString());
 			}
 		}
 
@@ -1038,7 +1044,7 @@ async Task ReadResponseDataAsync()
 				}
 			}
 		}
-		#endif
+#endif
 		bool UseOldHttpClient(string name)
 		{
 			if (Config.GetValueOf("useoldhttpclient", out string useOld) && useOld.StartsWith("y", StringComparison.OrdinalIgnoreCase))