Why key code 126 using {control down} not working by apple script on mac OSX 10.12.1 while it is working on OSX 10.12.3?

Question

tell application "System Events"
    key code 126 using {control down}
end tell

The above apple script is working for OSX 10.12.3 but not for OSX 10.12.1, Key code 126 for "Up" and "control with up" is shortcut for the mission control on osx. Please suggest.