I get the above error when I try to use my main font for the math letters. If I leave out the \sqrt[3]{2} bit, it works but gives a load of complaints about not having the OpenType feature 'Style=MathScriptScript' (+ssty) available in Calluna. (If you don't have Calluna: TeX Gyre Pagella shows the same behaviour.) What can I do?
\documentclass{article}
\usepackage{xltxtra}
\usepackage{fontspec}
\setmainfont{Calluna}%
\setsansfont{Calluna Sans}
\usepackage{unicode-math}
\setmathfont{TeX Gyre Termes Math}
% If one ore more of the following three lines are included ...
% \setmathfont[range=\mathup/{latin,Latin}]{Calluna}
% \setmathfont[range=\mathit/{latin,Latin}]{Calluna-Italic}
% \setmathfont[range=\mathbfup/{latin,Latin}]{Calluna-Bold}
\begin{document}\noindent\LARGE
% ... this would still work, but fontspec will nag about missing +ssty:
$a = -\frac{1}{2}$\\
% ... but this won't work at all:
$a = -\frac{1}{\sqrt[3]{2}}$
\end{document}
\setmathfont[range=\int]{TeX Gyre Termes Math}after all\setmathfontcommands. It seems to work. By the way, don't loadxltxtraunless you specifically need its features (which is unlikely); loadingunicode-mathis sufficient. – egreg Jun 25 '14 at 16:26unicode-math, that sets up some parameters based on the last declared math font. It probably should have separate\setmainmathfontand\setothermathfont, so it could take the needed parameters from the main font. – egreg Jun 25 '14 at 17:45