Default value of mandatory macro parameter cannot be used in WYSIWYG editor

It's apparently not possible to select the default value of a parameter when inserting a macro from the WYSIWYG editor.
Replication steps:

• Create a page Foo
• Create a mandatory WikiMacroParameterClass named "bar" in it with a default value "bar"
• Create a WikiMacroClass named "foo" containing the script:

  {{velocity}}$xcontext.macro.params.bar {{/velocity}}
  

• Edit the page in WYSIWYG mode
• Insert the macro with the default parameter value

Expected result:

• The macro can be inserted with default value

Obtained result:

• The macro cannot be inserted unless the value is different than the default value. Afterwards when editing the macro the value cannot be replaced by the default value.