Integral sign using eulervm and newpx

I’ve tried to load eulervm alongside newpxtext and newpxmath, and this has worked fine until I attempted to construct an integral using int. The integral sign simply doesn’t appear:

    documentclass{article}

    usepackage{newpxtext,newpxmath} 
    usepackage{eulervm}

    begin{document} 
    [int_a^b f(x), dx] 
    end{document}

Have I missed something?