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.

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?