diff --git a/stdwndclass_windows.go b/stdwndclass_windows.go
index f720051..fae357a 100644
--- a/stdwndclass_windows.go
+++ b/stdwndclass_windows.go
@@ -16,7 +16,10 @@ var (
 )
 
 func stdWndProc(hwnd _HWND, uMsg uint32, wParam _WPARAM, lParam _LPARAM) _LRESULT {
-//	sysData := getSysData(hwnd)
+	sysData := getSysData(hwnd)
+	if sysData == nil {	// not ready for events yet
+		goto defwndproc
+	}
 	switch uMsg {
 	case _WM_COMMAND:
 		id := wParam.LOWORD()
@@ -32,19 +35,21 @@ func stdWndProc(hwnd _HWND, uMsg uint32, wParam _WPARAM, lParam _LPARAM) _LRESUL
 		// TODO
 		return 0
 	case _WM_CLOSE:
-/*		if sysData.closing != nil {
+		if sysData.closing != nil {
 			sysData.closing <- struct{}{}
 		}
-*/		return 0
+		return 0
 	default:
-		r1, _, _ := defWindowProc.Call(
-			uintptr(hwnd),
-			uintptr(uMsg),
-			uintptr(wParam),
-			uintptr(lParam))
-		return _LRESULT(r1)
+		goto defwndproc
 	}
 	panic(fmt.Sprintf("stdWndProc message %d did not return: internal bug in ui library", uMsg))
+defwndproc:
+	r1, _, _ := defWindowProc.Call(
+		uintptr(hwnd),
+		uintptr(uMsg),
+		uintptr(wParam),
+		uintptr(lParam))
+	return _LRESULT(r1)
 }
 
 type _WNDCLASS struct {
diff --git a/sysdata_windows.go b/sysdata_windows.go
index 72ac46b..714f501 100644
--- a/sysdata_windows.go
+++ b/sysdata_windows.go
@@ -38,9 +38,6 @@ var classTypes = [nctypes]*classData{
 }
 
 func (s *sysData) make() (err error) {
-	sysDatasLock.Lock()
-	defer sysDatasLock.Unlock()
-
 	ret := make(chan uiret)
 	defer close(ret)
 	ct := classTypes[s.ctype]
diff --git a/sysdatacache_windows.go b/sysdatacache_windows.go
index 1bdb128..620d6ac 100644
--- a/sysdatacache_windows.go
+++ b/sysdatacache_windows.go
@@ -18,16 +18,18 @@ var (
 	sysDatasLock sync.Mutex
 )
 
-// MUST HAVE LOCKED BEFORE CALLING
 func addSysData(hwnd _HWND, s *sysData) {
+	sysDatasLock.Lock()
+	defer sysDatasLock.Unlock()
 	sysDatas[hwnd] = &sdcEntry{
 		s:			s,
 		members:		map[_HMENU]*sysData{},
 	}
 }
 
-// MUST HAVE LOCKED BEFORE CALLING
 func addIDSysData(hwnd _HWND, id _HMENU, s *sysData) {
+	sysDatasLock.Lock()
+	defer sysDatasLock.Unlock()
 	if ss, ok := sysDatas[hwnd]; ok {
 		ss.members[id] = s
 	}
@@ -40,7 +42,7 @@ func getSysData(hwnd _HWND) *sysData {
 	if ss, ok := sysDatas[hwnd]; ok {
 		return ss.s
 	}
-	panic(fmt.Sprintf("getting nonexistent HWND %d\n", hwnd))
+	return nil
 }
 
 func getIDSysData(hwnd _HWND, id _HMENU) *sysData {