diff --git a/dlls/mountmgr.sys/device.c b/dlls/mountmgr.sys/device.c
index 8b91be6333f..a3aa81cd389 100644
--- a/dlls/mountmgr.sys/device.c
+++ b/dlls/mountmgr.sys/device.c
@@ -938,10 +938,14 @@ static NTSTATUS WINAPI harddisk_ioctl( DEVICE_OBJECT *device, IRP *irp )
         break;
     }
     default:
-        FIXME( "unsupported ioctl %x\n", irpsp->Parameters.DeviceIoControl.IoControlCode );
+    {
+        ULONG code = irpsp->Parameters.DeviceIoControl.IoControlCode;
+        FIXME("Unsupported ioctl %x (device=%x access=%x func=%x method=%x)\n",
+              code, code >> 16, (code >> 14) & 3, (code >> 2) & 0xfff, code & 3);
         irp->IoStatus.u.Status = STATUS_NOT_SUPPORTED;
         break;
     }
+    }
 
     LeaveCriticalSection( &device_section );
     IoCompleteRequest( irp, IO_NO_INCREMENT );