natbib error only when using “round” option

Question

When I use sort&compress, everything works fine:

\usepackage[sort&compress]{natbib}
% ...
\bibliographystyle{unsrt}
\bibliography{refs}

I get the following error only when I include round in my natbib options:

\usepackage[sort&compress,round]{natbib}
% ...
\bibliographystyle{unsrt}
\bibliography{refs}

natbib Error: Bibliography not compatible with author-year citations

Does anyone know why this is? I've tried cleaning out temporary files and making from scratch.

Answer 1

The solution was to specify that the in-text citations should be numeric. I had (incorrectly) assumed that this would be default for sort&compress:

\usepackage[numbers,sort&compress,round]{natbib}