diff --git a/Library/MeterWindow.cpp b/Library/MeterWindow.cpp
index fd007bf7..277fa45d 100644
--- a/Library/MeterWindow.cpp
+++ b/Library/MeterWindow.cpp
@@ -177,6 +177,8 @@ MeterWindow::MeterWindow(const std::wstring& folderPath, const std::wstring& fil
 */
 MeterWindow::~MeterWindow()
 {
+	m_State = STATE_CLOSING;
+
 	if (!m_OnCloseAction.empty())
 	{
 		GetRainmeter().ExecuteCommand(m_OnCloseAction.c_str(), this);
@@ -383,6 +385,7 @@ void MeterWindow::RemoveWindowExStyle(LONG_PTR flag)
 */
 void MeterWindow::Deactivate()
 {
+	if (m_State == STATE_CLOSING) return;
 	m_State = STATE_CLOSING;
 
 	GetRainmeter().RemoveMeterWindow(this);
diff --git a/Library/Rainmeter.cpp b/Library/Rainmeter.cpp
index 737bb716..8df9d7c5 100644
--- a/Library/Rainmeter.cpp
+++ b/Library/Rainmeter.cpp
@@ -417,6 +417,7 @@ void Rainmeter::Finalize()
 
 	DeleteAllUnmanagedMeterWindows();
 	DeleteAllMeterWindows();
+	DeleteAllUnmanagedMeterWindows();  // Redelete unmanaged windows caused by OnCloseAction
 
 	delete m_TrayWindow;
 
@@ -981,10 +982,13 @@ void Rainmeter::DeleteAllMeterWindows()
 	while (it != m_MeterWindows.cend())
 	{
 		MeterWindow* mw = (*it).second;
-		m_MeterWindows.erase(it++);  // Remove before deleting MeterWindow
+		m_MeterWindows.erase(it);  // Remove before deleting MeterWindow
 
 		DialogManage::UpdateSkins(mw, true);
 		delete mw;
+
+		// Get next valid iterator (Fix for iterator invalidation caused by OnCloseAction)
+		it = m_MeterWindows.cbegin();
 	}
 
 	m_MeterWindows.clear();