Google Timeline Chart customized shape back to original due to interactivity

[Iris Huang]

For Google Timeline Chart, I need to customize the non duration activity (starting and ending at the same day). I apply the new style to make it ta square with both width and height 20px at event listener for ready event. 

However when interactivity enabled, mouse over the square, it just goes back to original bar with width maybe only 5px. 

How to prevent that behavior due to interactivity?