diff --git a/Renci.SshClient/Renci.SshNet/Security/Cryptography/DsaDigitalSignature.cs b/Renci.SshClient/Renci.SshNet/Security/Cryptography/DsaDigitalSignature.cs
index aebf86d3..87cdc506 100644
--- a/Renci.SshClient/Renci.SshNet/Security/Cryptography/DsaDigitalSignature.cs
+++ b/Renci.SshClient/Renci.SshNet/Security/Cryptography/DsaDigitalSignature.cs
@@ -164,7 +164,7 @@ namespace Renci.SshNet.Security.Cryptography
                     // Dispose managed ResourceMessages.
                     if (this._hash != null)
                     {
-                        this._hash.Dispose();
+                        this._hash.Clear();
                         this._hash = null;
                     }
                 }
diff --git a/Renci.SshClient/Renci.SshNet/Security/Cryptography/HMAC.cs b/Renci.SshClient/Renci.SshNet/Security/Cryptography/HMAC.cs
index f0457357..8152ff6d 100644
--- a/Renci.SshClient/Renci.SshNet/Security/Cryptography/HMAC.cs
+++ b/Renci.SshClient/Renci.SshNet/Security/Cryptography/HMAC.cs
@@ -153,5 +153,16 @@ namespace Renci.SshNet.Security.Cryptography
                 this._outerPadding[i] ^= this.KeyValue[i];
             }
         }
+
+        protected override void Dispose(bool disposing)
+        {
+            base.Dispose(disposing);
+
+            if (this._hash != null)
+            {
+                this._hash.Clear();
+                this._hash = null;
+            }
+        }
     }
 }
diff --git a/Renci.SshClient/Renci.SshNet/Session.cs b/Renci.SshClient/Renci.SshNet/Session.cs
index b4d6a646..56446e2b 100644
--- a/Renci.SshClient/Renci.SshNet/Session.cs
+++ b/Renci.SshClient/Renci.SshNet/Session.cs
@@ -1218,13 +1218,13 @@ namespace Renci.SshNet
             //  Dispose of old ciphers and hash algorithms
             if (this._serverMac != null)
             {
-                this._serverMac.Dispose();
+                this._serverMac.Clear();
                 this._serverMac = null;
             }
 
             if (this._clientMac != null)
             {
-                this._clientMac.Dispose();
+                this._clientMac.Clear();
                 this._clientMac = null;
             }