diff --git a/DearFTP/Connection/Commands/ListCommand.cs b/DearFTP/Connection/Commands/ListCommand.cs
index a75bc48..f202336 100644
--- a/DearFTP/Connection/Commands/ListCommand.cs
+++ b/DearFTP/Connection/Commands/ListCommand.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using System.Net.Security;
 using System.Text;
 
 namespace DearFTP.Connection.Commands
@@ -31,6 +32,8 @@ namespace DearFTP.Connection.Commands
 
             stream.Send(ResponseCode.FileStatusOK, "Listing coming.");
 
+            dataConnection.Authenticate();
+
             string path = null;
             bool humanReadable = false;
 
diff --git a/DearFTP/Connection/Commands/ListMachineCommand.cs b/DearFTP/Connection/Commands/ListMachineCommand.cs
index 0db2413..9100137 100644
--- a/DearFTP/Connection/Commands/ListMachineCommand.cs
+++ b/DearFTP/Connection/Commands/ListMachineCommand.cs
@@ -3,6 +3,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Net.Security;
 
 namespace DearFTP.Connection.Commands
 {
@@ -71,6 +72,8 @@ namespace DearFTP.Connection.Commands
 
             stream.Send(ResponseCode.FileStatusOK, "Listing coming.");
 
+            dataConnection.Authenticate();
+
             var dataStream = new FtpStream(dataConnection.Stream);
 
             foreach (var info in infos)
diff --git a/DearFTP/Connection/Commands/RetrieveCommand.cs b/DearFTP/Connection/Commands/RetrieveCommand.cs
index 6c730fa..a9f8b98 100644
--- a/DearFTP/Connection/Commands/RetrieveCommand.cs
+++ b/DearFTP/Connection/Commands/RetrieveCommand.cs
@@ -38,6 +38,8 @@ namespace DearFTP.Connection.Commands
 
             stream.Send(ResponseCode.FileStatusOK, "File coming.");
 
+            dataConnection.Authenticate();
+
             if (dataConnection.IsTlsProtected && !dataConnection.IsAvailable)
             {
                 stream.Send(ResponseCode.DataConnectionOpenError, "Passive mode not activated.");
diff --git a/DearFTP/Connection/Commands/StoreCommand.cs b/DearFTP/Connection/Commands/StoreCommand.cs
index a105029..5bfb850 100644
--- a/DearFTP/Connection/Commands/StoreCommand.cs
+++ b/DearFTP/Connection/Commands/StoreCommand.cs
@@ -49,6 +49,8 @@ namespace DearFTP.Connection.Commands
 
             stream.Send(ResponseCode.FileStatusOK, "Waiting file.");
 
+            dataConnection.Authenticate();
+
             if (dataConnection.IsTlsProtected && !dataConnection.IsAvailable)
             {
                 stream.Send(ResponseCode.DataConnectionOpenError, "Passive mode not activated.");
diff --git a/DearFTP/Connection/DynamicDataConnection.cs b/DearFTP/Connection/DynamicDataConnection.cs
index 3f017d5..17d5396 100644
--- a/DearFTP/Connection/DynamicDataConnection.cs
+++ b/DearFTP/Connection/DynamicDataConnection.cs
@@ -64,10 +64,7 @@ namespace DearFTP.Connection
 
                 if (IsTlsProtected)
                 {
-                    var sslStream = new SslStream(_client.GetStream(), false);
-                    sslStream.AuthenticateAsServer(FtpServer.Instance.Configuration.Tls.X509Certificate, false, true);
-
-                    Stream = sslStream;
+                    Stream = new SslStream(_client.GetStream(), false);
                 }
                 else
                 {
@@ -76,6 +73,14 @@ namespace DearFTP.Connection
             });
         }
 
+        public void Authenticate()
+        {
+            if (IsTlsProtected)
+            {
+                ((SslStream)Stream).AuthenticateAsServer(FtpServer.Instance.Configuration.Tls.X509Certificate, false, true);
+            }
+        }
+
         public void ActivateTls()
         {
             IsTlsProtected = true;
diff --git a/DearFTP/Connection/IDataConnection.cs b/DearFTP/Connection/IDataConnection.cs
index 97df4dc..898e555 100644
--- a/DearFTP/Connection/IDataConnection.cs
+++ b/DearFTP/Connection/IDataConnection.cs
@@ -11,6 +11,7 @@ namespace DearFTP.Connection
 
         void Create();
         void AcceptClient();
+        void Authenticate();
         void ActivateTls();
         void DesactivateTls();
         void Close();
diff --git a/DearFTP/Connection/StaticDataConnection.cs b/DearFTP/Connection/StaticDataConnection.cs
index cb04f9f..9445360 100644
--- a/DearFTP/Connection/StaticDataConnection.cs
+++ b/DearFTP/Connection/StaticDataConnection.cs
@@ -66,10 +66,7 @@ namespace DearFTP.Connection
 
                 if (IsTlsProtected)
                 {
-                    var sslStream = new SslStream(_client.GetStream(), false);
-                    sslStream.AuthenticateAsServer(FtpServer.Instance.Configuration.Tls.X509Certificate, false, true);
-
-                    Stream = sslStream;
+                    Stream = new SslStream(_client.GetStream(), false);
                 }
                 else
                 {
@@ -78,6 +75,14 @@ namespace DearFTP.Connection
             });
         }
 
+        public void Authenticate()
+        {
+            if (IsTlsProtected)
+            {
+                ((SslStream)Stream).AuthenticateAsServer(FtpServer.Instance.Configuration.Tls.X509Certificate, false, true);
+            }
+        }
+
         public void ActivateTls()
         {
             IsTlsProtected = true;