Client-side VTextField doesn't accept input after setReadOnly(false) in IE

We have a custom client-side widget which we want to dynamically set read-only to true/false in a VTextField.
In Chrome this works like a charm. In IE11 the field refuses to accept input until we have tabbed out and back in again.

So:
User writes value in previous field, and tabs to our custom field
Change is sent to server.
Server sets our custom field to read-only == false
Our custom client-side connector sets VTextField.setReadOnly(false)
→ The VTextField has focus, but it doesn’t accept input in IE.

Any ideas?