diff --git a/lib/platform/CXWindowsScreen.cpp b/lib/platform/CXWindowsScreen.cpp
index b7a84a8a..677bfc54 100644
--- a/lib/platform/CXWindowsScreen.cpp
+++ b/lib/platform/CXWindowsScreen.cpp
@@ -1404,6 +1404,10 @@ CXWindowsScreen::mapKeyFromX(XKeyEvent* event) const
 		if (keysym == XK_ISO_Left_Tab) {
 			return kKeyLeftTab;
 		}
+		if (keysym == XK_ISO_Level3_Shift) {
+			// treat ISO_Level3_Shift as ModeSwitch
+			return kKeyModeSwitch;
+		}
 		return kKeyNone;
 
 	case 0xff00: