How do I ensure that a search committee won't contact my current colleagues (that are not references) to ask about me? I once applied to a job (in the US) where the search committee unexpectedly contacted one of my colleagues to ask about my job performance. This individual was not one of my references.

I had never heard of this practice before, and now that I'm considering applying elsewhere (outside of the US), I'm wondering if this is something that I can expect from search committees in Europe.

My question is similar to How do I keep my tenure track job search confidential?, but there's one main addition I'm seeking: how do I ask for confidentiality in the cover letter without sounding as if my colleagues would give them bad news? I worry that asking for confidentiality might give the impression that I'm trying to hide something about my job performance. On the contrary, I know my colleagues would say great things about me; I'm just not ready to let everyone know that I'm applying for jobs outside of the US.
I used the following language, and I think it had the desired effect.


  Because I am hoping to keep this search confidential, I request that
  you contact my references rather than my current colleagues at this
  time. If I were to become a finalist, I would of course expect and
  invite you to speak to my current department.