Change rest duration from e.g. semibreve to bar.

I imported some XML which all went well. Time signature is 4/4. Then I added a stave and on the new stave, which is correctly all empty bars, the semibreve rest sign all have a duration of "Bar" which is great. How can I edit the old staves with empty bars so that the semibreve rest sign also has a duration of "Bar" and not Semibreve?

Any ideas?