diff --git a/tex/header/stdmath.sty b/tex/header/stdmath.sty
index 698f773d1faf3c821ba3ecc4829803bb69afac82..9f8169062adfb0fd4f1e96ec30c00ea800bbe22e 100644
--- a/tex/header/stdmath.sty
+++ b/tex/header/stdmath.sty
@@ -73,7 +73,7 @@
 \RequirePackage{mathtools}    % for := (defined as)
 \RequirePackage{amsthm}                   % for theorems environments
 \RequirePackage{enumerate}                  % for different kind of numbering in enumerations
-\RequirePackage{mhchem}  % chemical formulars. Provides \ce
+\RequirePackage[version=4]{mhchem}  % chemical formulars. Provides \ce
 \RequirePackage[per-mode=fraction]{siunitx}  % provides nice typesetting for units and numbers
 
 % bibliography