diff --git a/PInvoke/CfgMgr32/CfgMgr32_3.cs b/PInvoke/CfgMgr32/CfgMgr32_3.cs
index 5d71ef13..264559f2 100644
--- a/PInvoke/CfgMgr32/CfgMgr32_3.cs
+++ b/PInvoke/CfgMgr32/CfgMgr32_3.cs
@@ -24,7 +24,7 @@ namespace Vanara.PInvoke
 		/// cref="Win32Error.ERROR_SUCCESS"/>. The callback should not return any other values.
 		/// </returns>
 		[UnmanagedFunctionPointer(CallingConvention.Winapi)]
-		public delegate Win32Error CM_NOTIFY_CALLBACK(HCMNOTIFICATION notify, [Optional] IntPtr context, CM_NOTIFY_ACTION action, in CM_NOTIFY_EVENT_DATA eventData, uint eventDataSize);
+		public delegate Win32Error CM_NOTIFY_CALLBACK(HCMNOTIFICATION notify, [Optional] IntPtr context, CM_NOTIFY_ACTION action, [In] IntPtr eventData, uint eventDataSize);
 
 		/// <summary>
 		/// A variable of ULONG type that supplies one of the following flag values that apply if the caller supplies a device instance identifier
@@ -1982,7 +1982,7 @@ namespace Vanara.PInvoke
 		// pNotifyContext );
 		[DllImport(Lib_Cfgmgr32, SetLastError = false, ExactSpelling = true)]
 		[PInvokeData("cfgmgr32.h", MSDNShortId = "NF:cfgmgr32.CM_Register_Notification")]
-		public static extern CONFIGRET CM_Register_Notification(in CM_NOTIFY_FILTER pFilter, [In, Optional] IntPtr pContext, CM_NOTIFY_CALLBACK pCallback, out SafeHCMNOTIFICATION pNotifyContext);
+		public static extern CONFIGRET CM_Register_Notification(in CM_NOTIFY_FILTER pFilter, [In, Optional] IntPtr pContext, [MarshalAs(UnmanagedType.FunctionPtr)] CM_NOTIFY_CALLBACK pCallback, out SafeHCMNOTIFICATION pNotifyContext);
 
 		/// <summary>
 		/// The <c>CM_Request_Device_Eject</c> function prepares a local device instance for safe removal, if the device is removable. If
diff --git a/UnitTests/PInvoke/CfgMgr32/CfgMgr32Tests.cs b/UnitTests/PInvoke/CfgMgr32/CfgMgr32Tests.cs
index ac056a46..73ddd56e 100644
--- a/UnitTests/PInvoke/CfgMgr32/CfgMgr32Tests.cs
+++ b/UnitTests/PInvoke/CfgMgr32/CfgMgr32Tests.cs
@@ -507,10 +507,11 @@ namespace Vanara.PInvoke.Tests
 		public void RegisterAllInterfacesTest()
 		{
 			CM_NOTIFY_CALLBACK callback = Notification;
-			CM_NOTIFY_FILTER allDev = CM_NOTIFY_FILTER.AllDevices;
-			Assert.That(CM_Register_Notification(allDev, default, callback, out SafeHCMNOTIFICATION context), Is.EqualTo(CONFIGRET.CR_SUCCESS));
-			context.Dispose();
 			GC.KeepAlive(callback);
+			Assert.That(CM_Register_Notification(CM_NOTIFY_FILTER.AllDevices, default, callback, out SafeHCMNOTIFICATION context), Is.EqualTo(CONFIGRET.CR_SUCCESS));
+			for (int i = 0; i < 200; i++)
+				System.Threading.Thread.Sleep(100);
+			context.Dispose();
 		}
 
 		[Test]
@@ -578,38 +579,29 @@ namespace Vanara.PInvoke.Tests
 				}
 		};
 
-		private Win32Error Notification(HCMNOTIFICATION notify, IntPtr context, CM_NOTIFY_ACTION action, in CM_NOTIFY_EVENT_DATA eventData, uint eventDataSize)
+		private Win32Error Notification(HCMNOTIFICATION notify, IntPtr context, CM_NOTIFY_ACTION action, IntPtr ed, uint eventDataSize)
 		{
-			switch (eventData.FilterType)
+			unsafe
 			{
-				case CM_NOTIFY_FILTER_TYPE.CM_NOTIFY_FILTER_TYPE_DEVICEHANDLE:
-					if (action == CM_NOTIFY_ACTION.CM_NOTIFY_ACTION_DEVICECUSTOMEVENT)
-						Debug.WriteLine($"Custom event {eventData.u.DeviceHandle.EventGuid}.");
-					break;
+				CM_NOTIFY_EVENT_DATA* eventData = (CM_NOTIFY_EVENT_DATA*)ed;
+				switch (eventData->FilterType)
+				{
+					case CM_NOTIFY_FILTER_TYPE.CM_NOTIFY_FILTER_TYPE_DEVICEHANDLE:
+						if (action == CM_NOTIFY_ACTION.CM_NOTIFY_ACTION_DEVICECUSTOMEVENT)
+							Debug.WriteLine($"Custom event {eventData->u.DeviceHandle.EventGuid}.");
+						break;
 
-				case CM_NOTIFY_FILTER_TYPE.CM_NOTIFY_FILTER_TYPE_DEVICEINSTANCE:
-					unsafe
-					{
-						fixed (char* p = eventData.u.DeviceInstance.InstanceId)
-						{
-							var instanceId = new string(p);
-							Debug.WriteLine($"Notification for {instanceId}: {action}");
-						}
-					}
-					break;
+					case CM_NOTIFY_FILTER_TYPE.CM_NOTIFY_FILTER_TYPE_DEVICEINSTANCE:
+						var instanceId = new string(eventData->u.DeviceInstance.InstanceId);
+						Debug.WriteLine($"Notification for {instanceId}: {action}");
+						break;
 
-				case CM_NOTIFY_FILTER_TYPE.CM_NOTIFY_FILTER_TYPE_DEVICEINTERFACE:
-					unsafe
-					{
-						fixed (char* p = eventData.u.DeviceInterface.SymbolicLink)
-						{
-							var symbolicLink = new string(p);
-							Debug.WriteLine($"Notification for {eventData.u.DeviceInterface.ClassGuid} linked {symbolicLink}: {action}");
-						}
-					}
-					break;
+					case CM_NOTIFY_FILTER_TYPE.CM_NOTIFY_FILTER_TYPE_DEVICEINTERFACE:
+						var symbolicLink = new string(eventData->u.DeviceInterface.SymbolicLink);
+						Debug.WriteLine($"Notification for {eventData->u.DeviceInterface.ClassGuid} linked {symbolicLink}: {action}");
+						break;
+				}
 			}
-
 			return Win32Error.ERROR_SUCCESS;
 		}
 	}