Expressions disappear on step

1. Create a new Qt Quick UI project.
2. In the project's main.qml file, replace "Qt.quit();" with some more lines of code:

   var i = 0;
   var j = 1;
   var x = 92;
   

3. Set a breakpoint at the first of these lines.
4. Start debugging the project and hit the breakpoint.
5. Right-click on i in Locals and Expression view and select "Add Expression Evaluator for i" from the context menu.
   i appears as an expression.
6. Step.
   "i" is gone.

I expected the expressions to be shown all the time so I can see them changing.