diff --git a/dlls/winmm/driver.c b/dlls/winmm/driver.c
index 8620fe698f2..feecc921220 100644
--- a/dlls/winmm/driver.c
+++ b/dlls/winmm/driver.c
@@ -129,7 +129,7 @@ LPWINE_DRIVER	DRIVER_FindFromHDrvr(HDRVR hDrvr)
 static inline LRESULT DRIVER_SendMessage(LPWINE_DRIVER lpDrv, UINT msg,
                                          LPARAM lParam1, LPARAM lParam2)
 {
-    LRESULT		ret = 0;
+    LRESULT		ret;
 
     TRACE("Before call32 proc=%p drvrID=%08lx hDrv=%p wMsg=%04x p1=%08lx p2=%08lx\n",
           lpDrv->lpDrvProc, lpDrv->dwDriverID, lpDrv, msg, lParam1, lParam2);
@@ -552,24 +552,28 @@ BOOL WINAPI DriverCallback(DWORD_PTR dwCallBack, DWORD uFlags, HDRVR hDev,
 			   DWORD wMsg, DWORD_PTR dwUser, DWORD_PTR dwParam1,
 			   DWORD_PTR dwParam2)
 {
+    BOOL ret = FALSE;
     TRACE("(%08lX, %s %04X, %p, %04X, %08lX, %08lX, %08lX)\n",
 	  dwCallBack, DRIVER_getCallback(uFlags), uFlags, hDev, wMsg, dwUser, dwParam1, dwParam2);
+    if (!dwCallBack)
+	return ret;
 
     switch (uFlags & DCB_TYPEMASK) {
     case DCB_NULL:
-	break;
+	/* Native returns FALSE = no notification, not TRUE */
+	return ret;
     case DCB_WINDOW:
-	PostMessageA((HWND)dwCallBack, wMsg, (WPARAM)hDev, dwParam1);
+	ret = PostMessageA((HWND)dwCallBack, wMsg, (WPARAM)hDev, dwParam1);
 	break;
     case DCB_TASK: /* aka DCB_THREAD */
-	PostThreadMessageA(dwCallBack, wMsg, (WPARAM)hDev, dwParam1);
+	ret = PostThreadMessageA(dwCallBack, wMsg, (WPARAM)hDev, dwParam1);
 	break;
     case DCB_FUNCTION:
-	if (dwCallBack)
-	    ((LPDRVCALLBACK)dwCallBack)(hDev, wMsg, dwUser, dwParam1, dwParam2);
+	((LPDRVCALLBACK)dwCallBack)(hDev, wMsg, dwUser, dwParam1, dwParam2);
+	ret = TRUE;
 	break;
     case DCB_EVENT:
-	SetEvent((HANDLE)dwCallBack);
+	ret = SetEvent((HANDLE)dwCallBack);
 	break;
 #if 0
         /* FIXME: for now only usable in mmsystem.dll16
@@ -601,8 +605,11 @@ BOOL WINAPI DriverCallback(DWORD_PTR dwCallBack, DWORD uFlags, HDRVR hDev,
 	WARN("Unknown callback type %d\n", uFlags & DCB_TYPEMASK);
 	return FALSE;
     }
-    TRACE("Done\n");
-    return TRUE;
+    if (ret)
+	TRACE("Done\n");
+    else
+	WARN("Notification failure\n");
+    return ret;
 }
 
 /******************************************************************
diff --git a/dlls/winmm/tests/midi.c b/dlls/winmm/tests/midi.c
index e40e1d746de..f02c4f0fd15 100644
--- a/dlls/winmm/tests/midi.c
+++ b/dlls/winmm/tests/midi.c
@@ -325,6 +325,19 @@ static void test_midiOut_device(UINT udev, HWND hwnd)
     rc = midiOutClose(hm);
     ok(!rc, "midiOutClose rc=%s\n", mmsys_error(rc));
     test_notification(hwnd, "midiOutClose", MOM_CLOSE, 0);
+
+    rc = midiOutOpen(&hm, udev, 0, (DWORD_PTR)MYCBINST, CALLBACK_WINDOW);
+    ok(!rc, "midiOutOpen(dev=%d) 0 CALLBACK_WINDOW rc=%s\n", udev, mmsys_error(rc));
+    /* PostMessage(hwnd=0) redirects to PostThreadMessage(GetCurrentThreadId())
+     * which PeekMessage((HWND)-1) queries. */
+    test_notification((HWND)-1, "midiOutOpen WINDOW->THREAD", 0, WHATEVER);
+    test_notification(hwnd, "midiOutOpen WINDOW", 0, WHATEVER);
+    if (!rc) {
+        rc = midiOutClose(hm);
+        ok(!rc, "midiOutClose rc=%s\n", mmsys_error(rc));
+        test_notification((HWND)-1, "midiOutClose WINDOW->THREAD", 0, WHATEVER);
+        test_notification(hwnd, "midiOutClose", 0, WHATEVER);
+    }
     test_notification(hwnd, "midiOut over", 0, WHATEVER);
 }