Duplicated ID for properties of type List - checkbox/radio on displaying two objects of the same type (same class) in edit mode

Steps to reproduce :
1. Create a class (ClassName) having 1 property of type list with Multiple Select and display type as being Checkbox
2. Add 2 objects of the type ClassName to a document
3. Display the 2 objects of that document in edit mode

You will notice that when checking a value for the property of object1, the corresponding value in object2 will be unchecked. That is because both checkboxes have the same id ("xwiki-form-" + propname + "-" + count).