Wrong syntax used when switching editor from CKEditor source mode

Steps to reproduce:

• Open a wiki, login, and switch to advanced user
• Create a page Foo with the following macro:

  {{box}}
  Hello world
  {{/box}}
  

• Open Foo with WYSIWYG editor
• Switch to source mode
• Use the edit dropdown to select "Edit wiki" while you're still in source mode editing
• When you've got the confirm window telling that you might loose data click "Leave page"

Expected result:

• The Wiki editor opens and you see:

  {{box}}
  Hello world
  {{/box}}
  

Obtained result:

• The wiki editor opens and you see:

  ~{~{box}} Hello world ~{~{/box}}