\documentclass[12pt]{article}‎

‎\usepackage{amssymb}‎‎
‎‎
‎\usepackage{MnSymbol}‎
\renewcommand{\emptyset}{\font\cmsy = cmsy10 at 10pt \hbox{\cmsy \char 59}}


‎\begin{document}‎
$\varnothing$ $\emptyset$

‎\end{document}