diff --git a/src/calibre/devices/mtp/windows/device.cpp b/src/calibre/devices/mtp/windows/device.cpp
index d7f63f7038..6fd65dc58d 100644
--- a/src/calibre/devices/mtp/windows/device.cpp
+++ b/src/calibre/devices/mtp/windows/device.cpp
@@ -12,15 +12,13 @@ using namespace wpd;
 static void
 dealloc(Device* self)
 {
-    if (self->pnp_id != NULL) free(self->pnp_id);
-    self->pnp_id = NULL;
+	self->pnp_id.release();
+    if (self->bulk_properties) self->bulk_properties.Release();
 
-    if (self->bulk_properties != NULL) { self->bulk_properties->Release(); self->bulk_properties = NULL; }
-
-    if (self->device != NULL) {
+    if (self->device) {
         Py_BEGIN_ALLOW_THREADS;
-        self->device->Close(); self->device->Release();
-        self->device = NULL;
+        self->device->Close();
+		self->device.Release();
         Py_END_ALLOW_THREADS;
     }
 
@@ -32,28 +30,21 @@ dealloc(Device* self)
 static int
 init(Device *self, PyObject *args, PyObject *kwds)
 {
-    PyObject *pnp_id;
     int ret = -1;
-
-    if (!PyArg_ParseTuple(args, "O", &pnp_id)) return -1;
-
-    self->pnp_id = unicode_to_wchar(pnp_id);
-    if (self->pnp_id == NULL) return -1;
-
-    self->bulk_properties = NULL;
-
+    if (!PyArg_ParseTuple(args, "O&", py_to_wchar_no_none, &self->pnp_id)) return -1;
+    self->bulk_properties.Release();
     CComPtr<IPortableDeviceValues> client_information = get_client_information();
     if (client_information) {
-        self->device = open_device(self->pnp_id, client_information);
-        if (self->device != NULL) {
-            self->device_information = get_device_information(self->device, &(self->bulk_properties));
-            if (self->device_information != NULL) {
-                ret = 0;
-            }
-
+        self->device = open_device(self->pnp_id.ptr(), client_information);
+        if (self->device) {
+			IPortableDevicePropertiesBulk *bulk_properties = NULL;
+            self->device_information = get_device_information(self->device, &bulk_properties);
+            if (self->device_information) {
+				ret = 0;
+				self->bulk_properties = bulk_properties;
+			}
         }
     }
-
     return ret;
 }
 
diff --git a/src/calibre/devices/mtp/windows/device_enumeration.cpp b/src/calibre/devices/mtp/windows/device_enumeration.cpp
index dd4435ed25..ecc085af89 100644
--- a/src/calibre/devices/mtp/windows/device_enumeration.cpp
+++ b/src/calibre/devices/mtp/windows/device_enumeration.cpp
@@ -10,14 +10,13 @@
 namespace wpd {
 
 IPortableDeviceValues *get_client_information() { // {{{
-    IPortableDeviceValues *client_information;
     HRESULT hr;
 
     ENSURE_WPD(NULL);
+    CComPtr<IPortableDeviceValues> client_information;
 
     Py_BEGIN_ALLOW_THREADS;
-    hr = CoCreateInstance(CLSID_PortableDeviceValues, NULL,
-            CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&client_information));
+	hr = client_information.CoCreateInstance(CLSID_PortableDeviceValues, NULL, CLSCTX_INPROC_SERVER);
     Py_END_ALLOW_THREADS;
     if (FAILED(hr)) { hresult_set_exc("Failed to create IPortableDeviceValues", hr); return NULL; }
 
@@ -43,7 +42,7 @@ IPortableDeviceValues *get_client_information() { // {{{
     hr = client_information->SetUnsignedIntegerValue(WPD_CLIENT_SECURITY_QUALITY_OF_SERVICE, SECURITY_IMPERSONATION);
     Py_END_ALLOW_THREADS;
     if (FAILED(hr)) { hresult_set_exc("Failed to set quality of service", hr); return NULL; }
-    return client_information;
+    return client_information.Detach();
 } // }}}
 
 IPortableDevice *open_device(const wchar_t *pnp_id, CComPtr<IPortableDeviceValues> &client_information) { // {{{
@@ -207,7 +206,8 @@ end:
     return ans;
 } // }}}
 
-PyObject* get_device_information(IPortableDevice *device, IPortableDevicePropertiesBulk **pb) { // {{{
+PyObject*
+get_device_information(CComPtr<IPortableDevice> &device, IPortableDevicePropertiesBulk **pb) { // {{{
     IPortableDeviceContent *content = NULL;
     IPortableDeviceProperties *properties = NULL;
     IPortableDevicePropertiesBulk *properties_bulk = NULL;
diff --git a/src/calibre/devices/mtp/windows/global.h b/src/calibre/devices/mtp/windows/global.h
index 8baee04bff..8d9de83d5f 100644
--- a/src/calibre/devices/mtp/windows/global.h
+++ b/src/calibre/devices/mtp/windows/global.h
@@ -40,11 +40,10 @@ extern ClientInfo client_info;
 typedef struct {
     PyObject_HEAD
     // Type-specific fields go here.
-    wchar_t *pnp_id;
-    IPortableDevice *device;
+    wchar_raii pnp_id;
+    CComPtr<IPortableDevice> device;
     PyObject *device_information;
-    IPortableDevicePropertiesBulk *bulk_properties;
-
+    CComPtr<IPortableDevicePropertiesBulk> bulk_properties;
 } Device;
 extern PyTypeObject DeviceType;
 
@@ -56,7 +55,7 @@ int pump_waiting_messages();
 
 extern IPortableDeviceValues* get_client_information();
 extern IPortableDevice* open_device(const wchar_t *pnp_id, CComPtr<IPortableDeviceValues> &client_information);
-extern PyObject* get_device_information(IPortableDevice *device, IPortableDevicePropertiesBulk **bulk_properties);
+extern PyObject* get_device_information(CComPtr<IPortableDevice> &device, IPortableDevicePropertiesBulk **bulk_properties);
 extern PyObject* get_filesystem(IPortableDevice *device, const wchar_t *storage_id, IPortableDevicePropertiesBulk *bulk_properties, PyObject *callback);
 extern PyObject* get_file(IPortableDevice *device, const wchar_t *object_id, PyObject *dest, PyObject *callback);
 extern PyObject* create_folder(IPortableDevice *device, const wchar_t *parent_id, const wchar_t *name);
diff --git a/src/calibre/devices/mtp/windows/wpd.cpp b/src/calibre/devices/mtp/windows/wpd.cpp
index 9355e0bfea..b34082ce8a 100644
--- a/src/calibre/devices/mtp/windows/wpd.cpp
+++ b/src/calibre/devices/mtp/windows/wpd.cpp
@@ -131,7 +131,7 @@ wpd_enumerate_devices(PyObject *self, PyObject *args) {
 static PyObject *
 wpd_device_info(PyObject *self, PyObject *args) {
     PyObject *ans = NULL;
-    IPortableDevice *device = NULL;
+    CComPtr<IPortableDevice> device = NULL;
 
     ENSURE_WPD(NULL);
 
@@ -142,12 +142,10 @@ wpd_device_info(PyObject *self, PyObject *args) {
     CComPtr<IPortableDeviceValues> client_information = get_client_information();
     if (client_information) {
         device = open_device(pnp_id.ptr(), client_information);
-        if (device != NULL) {
-            ans = get_device_information(device, NULL);
-        }
+        if (device) ans = get_device_information(device, NULL);
     }
 
-    if (device != NULL) {device->Close(); device->Release();}
+    if (device) device->Close();
     return ans;
 } // }}}