diff --git a/Properties/AssemblyVersion.cs b/Properties/AssemblyVersion.cs
index 9a57bac..9bd3b02 100644
--- a/Properties/AssemblyVersion.cs
+++ b/Properties/AssemblyVersion.cs
@@ -10,5 +10,5 @@
 
 using System.Reflection;
 
-[assembly: AssemblyVersion("0.5.1.9")]
-[assembly: AssemblyInformationalVersion("0.5.1.9 Alpha")]
\ No newline at end of file
+[assembly: AssemblyVersion("0.5.1.10")]
+[assembly: AssemblyInformationalVersion("0.5.1.10 Alpha")]
\ No newline at end of file
diff --git a/WMI/WmiProvider.cs b/WMI/WmiProvider.cs
index 6e78df8..8456d56 100644
--- a/WMI/WmiProvider.cs
+++ b/WMI/WmiProvider.cs
@@ -5,7 +5,8 @@
   file, You can obtain one at http://mozilla.org/MPL/2.0/.
  
   Copyright (C) 2009-2010 Paul Werelds <paul@werelds.net>
-	
+	Copyright (C) 2012 Michael Möller <mmoeller@openhardwaremonitor.org>
+
 */
 
 using System;
@@ -102,6 +103,9 @@ namespace OpenHardwareMonitor.WMI {
         item => item.Identifier == identifier.ToString()
       );
 
+      if (instanceIndex == -1)
+        return;
+
       try {
         Instrumentation.Revoke(activeInstances[instanceIndex]);
       } catch (Exception) { }