diff --git a/Pop3Client.cs b/Pop3Client.cs
index 97a5c05..3909068 100644
--- a/Pop3Client.cs
+++ b/Pop3Client.cs
@@ -15,7 +15,10 @@ internal override void OnLogin(string username, string password) {
         }
 
         internal override void OnLogout() {
-            SendCommand("QUIT");
+            if (_Stream != null)
+            {
+                SendCommand("QUIT");
+            }
         }
 
         internal override void CheckResultOK(string result) {
diff --git a/TextClient.cs b/TextClient.cs
index 5688c36..8d1af8e 100644
--- a/TextClient.cs
+++ b/TextClient.cs
@@ -122,7 +122,7 @@ public void Disconnect() {
         _Stream.Dispose();
         _Stream = null;
       }
-      if (!_ReadThread.Join(2000)) {
+      if (_ReadThread != null && !_ReadThread.Join(2000)) {
         _ReadThread.Abort();
       }
     }