diff --git a/tex/header/stdmath.sty b/tex/header/stdmath.sty
index 2d7d4b3d7cb277b2080aaf867274455de713d7d4..e54037a68d842e3a8c3eee916b68be01f341b03e 100644
--- a/tex/header/stdmath.sty
+++ b/tex/header/stdmath.sty
@@ -131,7 +131,7 @@
 \newcommand{\N}{\mathbb{N}}             % natural numbers
 \newcommand{\Q}{\mathbb{Q}}             % rationals
 \newcommand{\R}{\mathbb{R}}             % reals
-\newcommand{\C}{\mathbb{C}}             % complex numbers
+% \newcommand{\C}{\mathbb{C}}             % complex numbers  % does not work, is already defined
 \newcommand{\K}{\mathbb{K}}             % a field
 
 \newcommand{\im}{\ensuremath{\mathrm{i}}}       % imaginary number sqrt(-1)