diff --git a/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.cpp b/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.cpp
index 8d3c9b3b8..1f5b59895 100644
--- a/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.cpp
+++ b/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.cpp
@@ -214,6 +214,8 @@ namespace s3d
 
 	Array<KeyEvent> CKeyboard::getEvents() const noexcept
 	{
+		std::lock_guard lock{ m_eventMutex };
+
 		return m_events;
 	}
 
diff --git a/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.hpp b/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.hpp
index ad618a3e6..40a17c78e 100644
--- a/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.hpp
+++ b/Siv3D/src/Siv3D-Platform/WindowsDesktop/Siv3D/Keyboard/CKeyboard.hpp
@@ -62,7 +62,7 @@ namespace s3d
 
 		//////
 		//
-		std::mutex m_eventMutex;
+		mutable std::mutex m_eventMutex;
 
 		uint32 m_eventIndex = 0;