diff --git a/SMBLibrary/Client/SMB1Client.cs b/SMBLibrary/Client/SMB1Client.cs
index 01b34c5..12ceffd 100644
--- a/SMBLibrary/Client/SMB1Client.cs
+++ b/SMBLibrary/Client/SMB1Client.cs
@@ -236,6 +236,11 @@ namespace SMBLibrary.Client
 
         public NTStatus Logoff()
         {
+            if (!m_isConnected)
+            {
+                throw new InvalidOperationException("A login session must be successfully established before attempting logoff");
+            }
+
             LogoffAndXRequest request = new LogoffAndXRequest();
             TrySendMessage(request);
 
diff --git a/SMBLibrary/Client/SMB2Client.cs b/SMBLibrary/Client/SMB2Client.cs
index 0031408..9fc83df 100644
--- a/SMBLibrary/Client/SMB2Client.cs
+++ b/SMBLibrary/Client/SMB2Client.cs
@@ -162,6 +162,11 @@ namespace SMBLibrary.Client
 
         public NTStatus Logoff()
         {
+            if (!m_isConnected)
+            {
+                throw new InvalidOperationException("A login session must be successfully established before attempting logoff");
+            }
+
             LogoffRequest request = new LogoffRequest();
             TrySendCommand(request);