What should I do with a Kanban-item that fails test?

I have a basic Kanban-board, with a handover between Developer and Test:

----------------------------------------------------
| To Do | Ready |         Develop    | Test | Done |
|       |       | In Progress | Done |      |      |

Assume that I have put some limits on the board. What should I do if an item fails the test? It is not the testers job to actually fix the mistake, so as I see it, there is no way it can go to "Done". I want the tester to put it back in "Ready", but that is going to excede the limit an that. If the tester demotes an item from "Ready" to "To Do" he is basically undoing the prioritizing of the PO.

My soultion so far is to be okay with exceding the limit on "Ready", mark the items that have failed tests, and make them a priority.

Any other ideas?

Solution

I'd split Ready state to Re-Open and Ready. In this case you can clearly separate items that need re-work and new items. Items that need re-work usually should be handled first, so it will be clear to developers what is new and what is returned from Testing phase.