diff --git a/Program.cs b/Program.cs
index a3b74db..5119737 100644
--- a/Program.cs
+++ b/Program.cs
@@ -17,6 +17,10 @@ class Program
     static string PASS = "pass";
     static readonly string UPSTREAM_USER = ResolveUpstreamUser();
     static readonly string UPSTREAM_PASS = Environment.GetEnvironmentVariable("UPSTREAM_PASS") ?? string.Empty;
+    static readonly bool FORCE_UPSTREAM_BASIC = string.Equals(
+        Environment.GetEnvironmentVariable("FORCE_UPSTREAM_BASIC"),
+        "1",
+        StringComparison.OrdinalIgnoreCase);
     static readonly string UPSTREAM_PROXY_AUTH_HEADER = BuildUpstreamProxyAuthHeader();
     static long _connectionSeq;
 
@@ -30,7 +34,7 @@ class Program
         Log.Info($"login: {USER}");
         Log.Info($"pass : {PASS}");
         Log.Info($"upstream auth user: {UPSTREAM_USER}");
-        Log.Info("upstream auth pass: <empty>");
+        Log.Info($"force upstream basic: {(FORCE_UPSTREAM_BASIC ? "on" : "off")}");
 
         var listener = new TcpListener(IPAddress.Any, port);
         listener.Start();
@@ -424,14 +428,18 @@ class Program
 
     static string BuildUpstreamProxyAuthHeader()
     {
+        if (!FORCE_UPSTREAM_BASIC)
+            return string.Empty;
+
         if (string.IsNullOrWhiteSpace(UPSTREAM_USER))
         {
-            Log.Warn("UPSTREAM_USER is empty; upstream Proxy-Authorization is disabled");
+            Log.Warn("FORCE_UPSTREAM_BASIC=1 but UPSTREAM_USER is empty; upstream Basic auth is disabled");
             return string.Empty;
         }
 
         string pass = UPSTREAM_PASS ?? string.Empty;
         string encoded = Convert.ToBase64String(Encoding.ASCII.GetBytes($"{UPSTREAM_USER}:{pass}"));
+        Log.Info("Upstream Basic auth header enabled");
         return $"Proxy-Authorization: Basic {encoded}\r\n";
     }
 
diff --git a/run.bat b/run.bat
index b615fa5..6b5a6e0 100644
--- a/run.bat
+++ b/run.bat
@@ -12,10 +12,12 @@ if not exist "%EXE%" (
 set "UPSTREAM_PROXY=proxy.syktsu.ru:3128"
 set "UPSTREAM_USER=%USERNAME%"
 set "UPSTREAM_PASS="
+set "FORCE_UPSTREAM_BASIC=0"
 
 echo [run] UPSTREAM_PROXY=%UPSTREAM_PROXY%
 echo [run] UPSTREAM_USER=%UPSTREAM_USER%
 echo [run] UPSTREAM_PASS is empty
+echo [run] FORCE_UPSTREAM_BASIC=%FORCE_UPSTREAM_BASIC%
 echo [run] Starting proxy...
 
 "%EXE%"