diff --git a/platform/CXWindowsScreen.cpp b/platform/CXWindowsScreen.cpp
index 4e88b5ed..4f223569 100644
--- a/platform/CXWindowsScreen.cpp
+++ b/platform/CXWindowsScreen.cpp
@@ -387,7 +387,10 @@ CXWindowsScreen::processEvent(XEvent* xevent)
 	}
 
 	// let screen saver have a go
-	m_screenSaver->processEvent(xevent);
+	{
+		CLock lock(&m_mutex);
+		m_screenSaver->processEvent(xevent);
+	}
 
 	return false;
 }
diff --git a/platform/CXWindowsScreenSaver.h b/platform/CXWindowsScreenSaver.h
index 95eb9830..c97eba39 100644
--- a/platform/CXWindowsScreenSaver.h
+++ b/platform/CXWindowsScreenSaver.h
@@ -16,7 +16,7 @@ class CXWindowsScreenSaver : public IScreenSaver {
 public:
 	// note -- the caller must ensure that Display* passed to c'tor isn't
 	// being used in another call to Xlib when calling any method on this
-	// object (including during the c'tor and d'tor) except processEvent().
+	// object (including during the c'tor and d'tor).
 	CXWindowsScreenSaver(CXWindowsScreen*, Display*);
 	virtual ~CXWindowsScreenSaver();