Unable to remove instance type from launch template

I created a launch template with a particular instance type defined. Later, I realized that I shouldn't have included the instance type in the template as it is better to specify template type with ASG or during individual launch. However, I am now unable to modify the launch template and remove the instance type. The steps I am following are:

• create a new version of launch template
• Go to Instance Type -> Select "Don't include in launch template"

However, the previously selected instance type remains selected and it never goes back to "Don't include in launch template" selection. I think this is a bug.