diff --git a/src/calibre/gui2/tts/windows.py b/src/calibre/gui2/tts/windows.py
index befe545f9e..8ed3076fb6 100644
--- a/src/calibre/gui2/tts/windows.py
+++ b/src/calibre/gui2/tts/windows.py
@@ -18,17 +18,19 @@ class Client:
         self.current_callback = None
 
     def __del__(self):
-        self.sp_voice.shutdown_event_loop()
-        self.events_thread.join(5)
-        self.sp_voice = None
+        if self.sp_voice is not None:
+            self.sp_voice.shutdown_event_loop()
+            self.events_thread.join(5)
+            self.sp_voice = None
     shutdown = __del__
 
     def wait_for_events(self):
         while True:
             if self.sp_voice.wait_for_event() is False:
                 break
-            if self.current_callback is not None:
-                self.current_callback()
+            c = self.current_callback
+            if c is not None:
+                c()
 
     def get_events(self):
         from calibre_extensions.winsapi import SPEI_TTS_BOOKMARK, SPEI_START_INPUT_STREAM, SPEI_END_INPUT_STREAM
diff --git a/src/calibre/utils/windows/winsapi.cpp b/src/calibre/utils/windows/winsapi.cpp
index b7efd088ff..e76039a391 100644
--- a/src/calibre/utils/windows/winsapi.cpp
+++ b/src/calibre/utils/windows/winsapi.cpp
@@ -340,7 +340,7 @@ Voice_shutdown_event_loop(Voice *self, PyObject *args) {
 }
 
 static PyObject*
-get_events(Voice *self, PyObject *args) {
+Voice_get_events(Voice *self, PyObject *args) {
     HRESULT hr;
     const ULONG asz = 32;
     ULONG num_events;
@@ -383,9 +383,9 @@ get_events(Voice *self, PyObject *args) {
 }
 
 static PyObject*
-Voice_wait_for_event(Voice *self, PyObject *callback) {
-    if (!PyCallable_Check(callback)) { PyErr_SetString(PyExc_TypeError, "callback object is not callable"); return NULL; }
+Voice_wait_for_event(Voice *self, PyObject *args) {
     const HANDLE handles[2] = {self->shutdown_events_thread, self->events_available};
+    DWORD ev;
     Py_BEGIN_ALLOW_THREADS;
     ev = WaitForMultipleObjects(2, handles, true, INFINITE);
     Py_END_ALLOW_THREADS;
@@ -420,7 +420,7 @@ static PyMethodDef Voice_methods[] = {
     M(set_current_sound_output, METH_VARARGS),
 
     M(shutdown_event_loop, METH_NOARGS),
-    M(wait_for_event, METH_O),
+    M(wait_for_event, METH_NOARGS),
     M(get_events, METH_NOARGS),
     {NULL, NULL, 0, NULL}
 };